Japy Freres Movement Repair: Timing Marks, Strike Train, and Barrel Diagnosis

Japy Freres movements represent some of the finest examples of nineteenth-century French clock manufacturing, and working on them rewards the clock repair technician who takes time to understand the specific conventions French makers used rather than assuming the mechanisms follow the same logic as German or American contemporaries. The round movement platform commonly found in French mantel clocks from this period uses assembly timing marks, a smooth-faced snail cam for hour count determination, a count wheel or rack strike mechanism depending on model, and a Brocot suspension regulator for fine rate adjustment — each of these features has specific characteristics that differ from what you may encounter in other clock traditions. Getting the timing marks aligned correctly at assembly, understanding why the rack tail will jam against a smooth snail when the strike train is unwound, and knowing how to diagnose and repair damaged barrel teeth are the three most common areas where clock restoration of Japy Freres movements requires specific knowledge to avoid frustrating setbacks.

This guide covers the complete diagnostic and repair sequence for Japy Freres and similar French round movements — how the cannon pinion, minute wheel, and hour wheel timing marks must be aligned during assembly and why misalignment causes the strike to produce wrong counts, what the smooth snail means for strike train setting compared to the stepped snails used in other traditions, how the rack tail interference at the twelve-to-one snail transition stops the clock when the strike runs down, how count wheel strike mechanisms get out of synchronization and what causes them to strike more or fewer blows than the time shown, how to evaluate and repair damaged barrel teeth, how to assess mainspring condition and the effect of sticky springs on strike reliability, and how the Brocot regulator changes effective suspension spring length for rate adjustment. Understanding these elements as a connected system produces more reliable repairs and fewer return visits.

Assembly Timing Marks on French Round Movements

Purpose of the Punch Marks

The punch marks stamped into the cannon pinion, minute wheel, and hour wheel of Japy Freres and similar French movements are assembly registration marks that ensure the motion work is assembled in the one specific gear mesh position where the strike trigger, the snail cam position, and the hands all agree about the current time. On a stepped snail movement the hour count is mechanically forced by the snail step depth, and minor misalignment in the motion work produces a predictable offset error that is relatively easy to diagnose and correct. On a smooth snail movement — where the snail face is a continuous slope rather than a series of distinct steps — the relationship between the motion work gear mesh and the snail position is critical because a smooth snail can produce any count from one to twelve depending on exactly where the rack tail lands, and misalignment of the timing marks will cause the clock to produce wrong counts that vary inconsistently as the snail rotates through different positions. The timing marks eliminate this ambiguity by specifying the one correct assembly position.

Understanding why smooth snail movements require these marks — and why stepping snail movements do not always mark their wheels — is the key to using them correctly. When the timing marks are properly aligned at assembly, the rack tail will land on the correct position of the smooth snail slope for each hour, producing the correct count consistently throughout the twelve-hour cycle. When the marks are misaligned, the snail position at each hour is shifted relative to what the motion work expects, causing the clock to produce counts that seem random or that are off by a consistent amount across all hours. Clock repair technicians who have worked primarily on stepped snail movements sometimes underestimate how critical correct assembly alignment is on smooth snail French clocks — the stepped snail is forgiving of moderate assembly misalignment while the smooth snail is not.

Correct Alignment Procedure for Cannon Pinion and Minute Wheel

Align the timing marks in a specific sequence beginning with the cannon pinion and minute wheel before installing the hour wheel. Visualize a straight line running through the center of the cannon pinion arbor and the center of the minute wheel arbor — this is the reference line for mark alignment. Install the cannon pinion with its timing mark pointing along this line directly toward the minute wheel center. The mark on the cannon pinion will typically be positioned between two teeth. Now place the minute wheel so that its timing mark also faces along the same line toward the cannon pinion, with the marked tooth of the minute wheel seated in the space between the two cannon pinion teeth that bracket the cannon pinion mark. Both marks should now be visible on the same line between the two arbor centers.

With the cannon pinion and minute wheel correctly meshed at their marks, install the hour wheel so that its timing mark points along the line toward the minute wheel pivot position. The minute cock can then be fitted and screwed in place, after which you can verify that all three marks are aligned along the same line before closing the movement. If the snail is mounted on the cannon pinion or hour pipe, it will cover the cannon pinion mark at the point where the rack tail engages — this is normal and does not prevent correct alignment because the minute wheel mark remains visible as a reference. After assembly, advance the hands to the hour and test the strike count at several hours across the full twelve-hour cycle to confirm the assembly marks have produced correct synchronization between the motion work and the smooth snail.

Strike Alignment Without Timing Marks

Some French movements arrive without visible timing marks — either because they were never marked, because the marks have become indistinct through cleaning or wear, or because the movement is a model that used a different synchronization method. For these movements, correct strike alignment is established by positioning the motion work at the moment the strike is triggered. Set the small center wheel to the position where the strike release lever has just dropped — this is the precise angular position where the strike trigger occurs. With the motion work in this position, the minute hand should point to twelve or six. Install the hour wheel so that the hour hand points to the correct hour for the strike that is about to execute. If the minute hand points to twelve, install the hour wheel at one of the twelve hour positions; if it points to six, install at a half-hour position. Verify the alignment by advancing through several hours and confirming correct count at each position before considering the assembly complete.

The Smooth Snail and Its Strike Implications

How the Smooth Snail Determines Hour Count

Unlike the stepped snail used in most rack-and-snail strike mechanisms — where each of twelve distinct steps locks the rack at a specific depth corresponding to a specific hour — the smooth snail used in many Japy Freres and other French movements presents a continuously sloped surface against which the rack tail rests. The depth at which the rack tail rests on this slope determines how many rack teeth are exposed for gathering, which determines how many blows are struck. Because the slope is continuous rather than stepped, the count produced is entirely dependent on the exact angular position of the snail at the moment the rack falls — there are no discrete mechanical stops to guarantee a correct count regardless of minor position variation. This design requires that the motion work and snail be correctly synchronized through the timing marks so that the snail presents exactly the right slope position at each hour.

The practical consequence for clock restoration is that a smooth snail movement reassembled without correct timing mark alignment may run and strike plausibly for a period — producing counts that appear approximately correct — before the accumulated angular error from incorrect mesh position causes the strike to produce noticeably wrong counts. This delayed symptom can mislead a technician into thinking the reassembly was correct until the error becomes large enough to be obvious, which may not happen until the clock has been returned to its owner. Always verify correct strike counts through the full twelve-hour cycle before considering a smooth snail French movement fully repaired, not just at a few hours that happen to fall on correct counts despite underlying misalignment.

Rack Tail Interference at the Twelve-to-One Snail Transition

French rack-and-snail movements with a smooth snail typically have a square or abrupt transition at the boundary between the twelve o'clock snail position and the one o'clock snail position — the point where the snail resets from its deepest position back to its shallowest. This transition is not a gentle slope but a vertical face, and the rack tail is designed to be lifted clear of this face by the rack hook before the snail rotates through it. When the strike train runs down completely — leaving the rack in its dropped position rather than in its lifted, locked position — the rack tail rests against the snail face in the operating position. If the clock continues to run time while the strike is unwound, the snail will eventually rotate until its vertical reset face comes around to meet the dropped rack tail. At this point, continued snail rotation is physically blocked by the rack tail, which jams the motion work and stops the clock. This is why a French round movement stops at approximately five minutes before one o'clock when the strike has been allowed to run down — the snail rotation is blocked at precisely the point where the twelve-to-one transition face contacts the rack tail.

The correct response to this situation is not to advance the minute hand forward — doing so will apply force to the jammed mechanism and risks breaking the minute hand at its collet. Instead, back the minute hand to approximately twenty minutes before the hour, then wind the strike train. In most cases the strike train will run briefly, the rack will be gathered back to its lifted position, and the mechanism will reset allowing the clock to run normally. Inform owners of French round movements that both the time train and strike train must be kept wound — allowing the strike to run completely down will stop the clock and require manual intervention to reset. This is normal behavior for this design and is not a defect, but it is a characteristic that owners often do not know about and that returns the clock to the bench unnecessarily when not communicated clearly after servicing.

Count Wheel Strike Getting Out of Synchronization

Some French movements including certain Japy Freres models use a count wheel strike mechanism rather than a rack-and-snail. The count wheel — a wheel with slots or notches at positions corresponding to the cumulative total of blows struck from one through twelve — controls strike termination by allowing the stop lever to fall into a slot when the correct number of blows has been struck. Unlike the rack-and-snail system where the strike count is reset at each hour by the snail position, the count wheel system accumulates counts sequentially and depends on the strike train always producing exactly the correct number of blows at each hour without any missed strikes or extra strikes. If the strike fails to trigger at any hour — because the lifting lever is not fully released, because the click spring is too stiff, or because sticky oil is preventing the trigger mechanism from moving freely — the count wheel advances by fewer positions than it should. On the next trigger, the count wheel is already in the wrong position and will stop the train at the wrong count. The error then accumulates with each subsequent missed trigger, causing the count to drift progressively further from the correct time shown on the dial.

Conversely, if the strike fails to stop at the correct count — because the stop lever is not engaging the count wheel slot cleanly, because the count wheel slot is worn, or because the strike train has too much momentum to stop promptly — the count wheel advances past the correct slot and the next strike will produce one or more extra blows. This error also accumulates progressively. Distinguish between the two failure modes by observing whether the clock strikes fewer blows than the time shown (missed trigger, sticky lift mechanism) or more blows than the time shown (count wheel overrun, worn stop lever engagement). Each cause requires a different correction and oiling alone will only address the sticky-trigger case — assembly problems and worn components require their own specific remedies.

Diagnosing and Repairing Damaged Barrel Teeth

Identifying Barrel Tooth Damage and Its Causes

The mainspring barrel in a French clock movement contains the mainspring and drives the first wheel of the time or strike train through teeth cut into the barrel perimeter. Barrel teeth in French movements are generally robust, and significant tooth damage — bent, worn, or broken teeth — is unusual compared to what is commonly seen in heavily worn American movements. When barrel tooth damage does occur in a French movement, the cause is almost always mechanical rather than simple wear: a loose barrel cap allowing the barrel to wobble on its arbor, a bent arbor on the second wheel creating intermittent jamming as the wheel mesh varies through one rotation, the barrel arbor itself having excessive play in its bushings allowing the barrel to shift position during operation, or the movement having been run with incorrect lubrication that caused the meshing surfaces to abrade rather than slide. Identifying and correcting the cause of the damage is essential — filing or dressing the teeth without finding the root cause will result in recurring damage.

Examine the mating pinion — the second wheel pinion that meshes with the barrel teeth — for corresponding wear on its leaves. If the barrel teeth are significantly damaged but the second wheel pinion leaves appear normal, the damage was likely caused by the barrel wobbling on its arbor rather than by tooth-on-tooth impact between barrel and pinion. If both barrel teeth and pinion leaves show damage, the misalignment between barrel and pinion centers was the cause, pointing to worn bushings or a bent arbor. Measure the barrel arbor diameter and the barrel cap internal diameter — in a healthy movement these should be closely matched with only a few hundredths of a millimeter of clearance. A gap of 0.1mm or more allows the barrel to tilt measurably on its arbor, producing the wobbling motion that causes uneven tooth contact and progressive tooth damage. The diagnostic test of installing only the barrel and second wheel between the plates and rotating the barrel slowly by hand while feeling for resistance will reveal the specific angular position where tight mesh or binding occurs.

Dressing Damaged Barrel Teeth

Light dressing of damaged barrel teeth — where individual teeth are bent slightly or have rough edges from impact — can restore serviceable function using a fine needle file or escapement file working carefully on each affected tooth. The goal is to restore the correct tooth profile allowing smooth mesh with the pinion leaves rather than to remove material broadly across the barrel perimeter. Work on one tooth at a time, removing only enough material to eliminate the burr or reshape the bent face, and check the mesh with the pinion after each tooth is dressed to confirm the profile is correct. Avoid aggressive filing that removes significant tooth height — a shortened barrel tooth will not transmit power as efficiently and will wear the opposing pinion leaf more rapidly than a correctly profiled tooth.

After dressing, install the barrel and second wheel together between the plates without other components and rotate the barrel through multiple full revolutions by hand, feeling for any remaining resistance at specific positions. A correctly dressed barrel will rotate smoothly through the full range with no perceptible variation in resistance. Identify any remaining tight spots and dress those specific teeth further before reassembling the complete movement. Note that French barrels make only approximately 2.5 full rotations per week of running time, which means that a problem affecting only a portion of the barrel circumference may not manifest during short bench tests — the barrel must complete at least one full rotation under running conditions to expose all potentially problematic tooth positions. Plan for a minimum three-day test run before considering barrel tooth repairs fully validated.

Mainspring Condition and Sticky Spring Problems

The mainspring in a French barrel must be clean, correctly lubricated, and free of cracks, kinks, or set — the permanent curvature that develops in a spring that has been compressed for an extended period without running. A sticky mainspring — one where the spring coils adhere to each other due to old dried lubricant — creates variable power delivery throughout the winding cycle, with the first few hours after winding providing normal power followed by declining power as the sticky coils resist uncoiling. This variable power delivery causes the strike train to run correctly when freshly wound but to produce slow, hesitant strikes or complete failures to trigger as the mainspring approaches its weaker end-of-run condition. Intermittent strike failure that correlates with how recently the clock was wound is a strong indicator of mainspring stickiness rather than a mechanical strike train fault.

Correct mainspring stickiness by removing the spring from the barrel, cleaning the spring thoroughly with an appropriate solvent to remove old lubricant from between the coils, and relubrication with a dedicated mainspring grease or clock spring lubricant applied sparingly along the full length of the spring before it is wound back into the barrel. Do not attempt to clean the mainspring while it remains in the barrel — oil applied into the barrel opening will not reach between the coils adequately and the cleaning will be incomplete. Full spring removal, cleaning, and relubrication is the correct procedure and, while more time-consuming than a barrel-in cleaning, is the only approach that reliably resolves sticky spring problems and prevents their recurrence within a reasonable service interval.

Minute Hand Adjustment and Motion Work Correction

Adjusting the Minute Hand Brass Bushing

French mantel clocks typically use a minute hand with a brass bushing — a small brass insert in the hand's center collet that engages the square of the minute arbor. This bushing can be rotated within the hand to adjust the angular position of the hand relative to the arbor square, providing a fine-tuning mechanism for hand position that does not require repositioning the entire motion work. When a clock strikes correctly at the twelve and six positions but the minute hand points slightly before or after twelve at the strike moment — as when the hand points at five minutes past twelve when the strike fires — adjusting the brass bushing is the correct solution rather than modifying the motion work assembly.

To adjust the bushing, insert a square needle file or small square-section screwdriver into the brass bushing to engage its square bore. Hold the center of the minute hand firmly with the other hand or secure the file in a bench vise. Carefully rotate the minute hand body counter-clockwise relative to the bushing by a small amount — the hand will move relative to the bushing while the bushing remains stationary on the arbor square. Work in small increments, checking the hand position after each adjustment, and be careful not to apply bending force to the hand during the adjustment. The goal is to have the hand point precisely to twelve when the strike triggers. This adjustment does not affect the internal motion work position and requires no reassembly of the movement — it is a hand position correction only.

Strike Registration Marks in the Strike Train

Beyond the motion work timing marks described earlier, French clock strike trains including those on Japy Freres movements often include registration marks in the strike train itself — particularly on the count wheel and its associated arbor, or on the pin wheel relative to the gathering pallet pinion. A long mark on the underside of the count wheel near the square hole, paired with a corresponding mark on one face of the square arbor it mounts to, ensures that the count wheel is installed at the one correct angular position where its slot pattern is synchronized with the motion work position. Installing the count wheel at a rotated position — possible because a square arbor offers four installation orientations — will cause the strike to produce systematically wrong counts from the moment of first assembly, typically off by a consistent amount that shifts as the count wheel rotates.

Similarly, pin wheel registration marks ensure that the fly pinion and gathering pallet are in correct phase with the pins that will trigger the bell hammer or gong, so that each strike blow occurs at the mechanically correct point in the strike train rotation. If a French movement has been disassembled and reassembled without observing these strike train marks, systematic strike count errors are predictable and should be corrected by identifying the marks on each component and reassembling at the marked positions before doing any other diagnostic work on the strike mechanism.

Brocot Regulator and Rate Adjustment

How the Brocot Regulator Works

The Brocot regulator — the rate adjustment mechanism named for Achille Brocot, the French clockmaker who developed it — is a device mounted at the top of the movement or dial that changes the effective length of the suspension spring by moving a pair of small curved cheeks or pins that embrace the spring, effectively shortening or lengthening the free-vibrating portion of the spring. A shorter effective spring length increases stiffness, which raises the pendulum's natural frequency and makes the clock run faster. A longer effective spring length decreases stiffness, lowering the frequency and slowing the clock. The adjustment is typically accessed through a small square key hole at the top of the dial, allowing rate adjustment without opening the case. Turning the Brocot key clockwise raises the rate; counter-clockwise lowers it.

The Brocot regulator is a fine-tuning tool with a limited adjustment range — it cannot compensate for a pendulum bob that is dramatically incorrectly positioned or a suspension spring of the wrong thickness. The correct approach for rate adjustment on a French clock with a Brocot regulator and an adjustable pendulum bob is to set the Brocot to approximately mid-range of its adjustment, then adjust the bob position so the clock keeps approximately correct time, and finally use the Brocot for the remaining fine adjustment to achieve accurate timekeeping. If the Brocot must be at its extreme position to keep the clock on rate, the bob position needs correction — the Brocot should be returned to mid-range, the bob repositioned to compensate for approximately half the remaining error, and the Brocot used for the final trim.

Suspension Spring Selection for French Movements

French mantel clocks including Japy Freres movements use suspension springs that are typically narrower and thinner than those found in American mantel clocks of comparable size, reflecting the finer tolerances and lighter pendulum weights characteristic of French clock design. Selecting the correct suspension spring requires matching both the width and thickness to the original spring dimensions — a spring that is too stiff will cause the clock to run fast and reduce pendulum amplitude, while a spring that is too flexible may allow excessive lateral pendulum movement that causes the pendulum to contact the case interior. When the original spring is unavailable as a reference, measure the suspension block slot dimensions to establish the maximum spring width, and estimate correct thickness from the pendulum bob weight and movement characteristics. French clock suspension springs are available from specialist clock parts suppliers and should be ordered by measured dimensions rather than by generic size designations that may vary between suppliers.

General Cleaning and Lubrication Considerations

French Movement Cleaning Sequence

Japy Freres and similar French movements benefit from thorough cleaning before any diagnostic or repair work because old oil and accumulated dirt are among the most common causes of intermittent strike failure, reduced amplitude, and rate irregularity in these movements. French movements are typically well-made with good pivot fit and generous wheel and pinion sizing, which means that when a properly cleaned and lubricated French movement does not run correctly, the problem is almost always a specific mechanical fault rather than generalized wear. Cleaning removes the diagnostic variable of contamination and allows you to evaluate the true mechanical condition of the movement with confidence that any remaining problems are genuine faults rather than lubrication effects.

Clean French movements using an appropriate clock cleaning solution, ultrasonic cleaner, or hand cleaning with appropriate solvents and peg wood, paying attention to the pivot holes, mainspring barrel, and count wheel or snail cam slots where old lubricant accumulates most heavily. Do not apply lubricant to the rack system gravity-driven components, the count wheel stop lever pivot, or the motion work pivots — these should run on clean polished surfaces. Apply appropriate clock oil to the time and strike train pivot holes, the barrel arbor bearings, and the escapement pallets and escape wheel pivot holes. Apply mainspring grease to the mainspring itself after removing it from the barrel for cleaning. A French movement serviced with correct cleaning and lubrication will typically run reliably for many years before requiring the next service.

Assessing Movement Condition on Acquisition

French movements acquired from family estates, thrift stores, or antique markets frequently present with unknown service histories and may show evidence of previous amateur repair attempts including incorrect lubrication on wheel teeth, replaced components that do not match the original specifications, bent pivots from careless disassembly, or modifications that seemed logical to a previous owner but created new problems. Approach each acquired French movement with a systematic inspection before attempting to run it — examine the barrel teeth and mating pinions for damage, check each pivot hole for wear or deformation, verify that the mainspring is intact and correctly installed, confirm that all strike train components are present and correctly positioned, and identify any obvious signs of previous work such as fresh file marks, replacement screws that do not match the original style, or components that appear to belong to a different movement. This preliminary assessment guides the repair sequence and prevents the frustration of performing a full service only to discover a fundamental mechanical problem that should have been addressed first.

FAQs

Why do Japy Freres movements have timing marks on the wheels?

The timing marks on the cannon pinion, minute wheel, and hour wheel of Japy Freres and similar French movements exist because these movements use a smooth-faced snail cam rather than a stepped snail to control the strike count. A smooth snail produces the correct count only when the snail is at exactly the right angular position for each hour, which requires the motion work to be assembled at one specific gear mesh position. The timing marks identify this position, ensuring that the strike count is correct throughout the twelve-hour cycle. Stepped snail movements are more tolerant of minor assembly variation because the steps mechanically enforce a limited set of rack depths; smooth snail movements have no such enforcement and require exact synchronization through the timing marks.

Why does my French clock stop at five minutes before one o'clock?

A French round movement stopping at approximately five to one almost always indicates that the strike train has run down completely, leaving the rack in its dropped position rather than lifted and locked by the rack hook. As the time train continues to advance the snail cam, the snail eventually rotates to its reset transition — the vertical face between the twelve o'clock position and the one o'clock position — which contacts the dropped rack tail and physically blocks further snail rotation, stopping the clock. The solution is to back the minute hand to approximately twenty minutes before the hour, then wind the strike train, which will allow the strike to run and reset the rack to the lifted position. Both trains must be kept wound in French movements of this design — the strike cannot be left unwound while the time train continues to run.

How do I correct a count wheel strike that is out of synchronization?

Resynchronizing a count wheel strike requires identifying whether the error is from under-striking (clock strikes fewer blows than the time shown, indicating missed triggers) or over-striking (clock strikes more blows than the time shown, indicating the train runs past the correct stop). For under-striking, clean the strike trigger mechanism and verify the lifting lever travels fully to release the strike — sticky oil on the lever pivot is the most common cause. For over-striking, examine the count wheel stop lever engagement with the count wheel slots and verify the fly is providing adequate braking to stop the train promptly. After correcting the root cause, the count wheel position must be reset to synchronize with the current time by advancing or retarding the count wheel to the correct slot position for the current hour.

Can I use a nail file to dress damaged barrel teeth?

A nail file can remove material from barrel teeth but is too coarse and too difficult to control precisely for restoration-quality barrel tooth dressing. A fine needle file or escapement file — properly held and used with light controlled strokes — provides better results with less risk of removing too much material or damaging the tooth profile on adjacent undamaged teeth. Work on one tooth at a time, remove only the minimum material needed to eliminate the damage, and check mesh with the mating pinion frequently. The goal is to restore the correct tooth profile for smooth mesh, not to make the teeth look new. After dressing, test the barrel through multiple full rotations by hand to confirm smooth operation before reassembling the movement.

What causes intermittent strike failure that gets worse as the clock runs down?

Intermittent strike failure that correlates with how recently the clock was wound — working correctly when freshly wound but failing or producing weak strikes after a day or two — strongly indicates a sticky mainspring. Old lubricant between the mainspring coils dries and causes the coils to adhere, producing normal power delivery when the spring is fully wound and the coils are under tension, but increasing resistance to uncoiling as the spring approaches its end-of-run condition. The correction requires removing the mainspring from the barrel, cleaning it thoroughly to remove all old lubricant from between the coils, and applying fresh mainspring grease before rewinding into the barrel. Surface cleaning of the barrel without removing the spring will not reach between the coils and will not solve the problem.

What is the Brocot regulator and how do I use it?

The Brocot regulator is a rate adjustment device mounted at the top of a French mantel clock that changes the effective vibrating length of the suspension spring by moving small curved cheeks or pins that embrace the spring. A shorter effective spring length makes the clock run faster; a longer effective length makes it run slower. It is adjusted through a small square key hole at the top of the dial — clockwise for faster, counter-clockwise for slower. Use it as a fine-tuning tool only: set it to mid-range, adjust the pendulum bob to get the clock approximately on rate, and then use the Brocot for the remaining fine correction. If the Brocot must be at an extreme position to keep correct time, the bob position needs adjustment first.

Why does my French clock strike the wrong count and how do I fix it?

Wrong strike count on a French movement is most often caused by incorrect assembly of the timing marks in the motion work, an incorrectly positioned count wheel, or in a smooth snail movement by misalignment between the motion work gear mesh and the snail position. Begin diagnosis by verifying that the timing marks on the cannon pinion, minute wheel, and hour wheel are correctly aligned at the one marked mesh position — reassemble at the marked positions if any doubt exists. If the count is wrong by a consistent amount at every hour, the count wheel or hour wheel installation is offset and needs correction. If the count is wrong by varying amounts at different hours, the smooth snail synchronization is incorrect and the motion work timing marks need to be realigned. Test through the full twelve-hour cycle after any correction to confirm all hours produce correct counts before returning the movement to the case.