Under the balance wheel, near the caliber number engraving, you may have seen what looks to be a laser etched code containing DM and XYZ.
DM means that the movement origin is from Sellita Watch Co (where else would it be from we’re not sure).
XYZ is a Sellita code (we’re not sure the meaning, comment below if you know)
As for the date part of the code, new movements produced in 2018 look like this:
DM18.1/XYZ = JAN+FEB
DM18.2/XYZ = MAR+APRIL
DM18.3/XYZ = MAY+JUNE
DM18.4/XYZ = JULY+AUG
DM18.5/XYZ = SEPT+OCT
DM18.6/XYZ = NOV+DEC
There is also a code for what Sellita refers to as “Renewed Movements”. The meaning of this still needs to be confirmed, but it appears that this is for movements that were sent back to Sellita for renewal. Perhaps brands are able to buy them at a discount. We still don’t know, but please check your movement for a two digit number starting with 2X. For reference:
A 2-digit customer service code is engraved to show that the movement has been renewed.
20 for 2020, 21 for 2021, etc.
Case study pics coming soon.
Official Sellita documentation states that the crown should be in the time setting position before being extracted. Use a 1mm screw-driver, avoid using tweezers or any other tool with a point because this could jam the setting lever and damage the setting lever spring.
Ratchet Wheel Issues:
The primary reason behind the evolution from SW200 to SW200-1 was to fix an issue with the teeth of the ratchet wheel breaking off, perhaps while hand-winding the movement. There are skeptics who question whether these problematic parts are a direct result of hand-winding, but as with many topics in the watch community, it is a topic that is debated between those who have experienced the issue (or repaired the issue) and those who have not. Likewise, experiences with the ETA 2824-2 having similar issues is also split with some saying they have experienced it, and others pointing to how ETA holds a patent for a ratchet wheel that is less prone to teeth stripping by design.
Regardless, the ratchet wheel teeth issue that was supposed to be remedied in the original SW200 is still experienced in the SW200-1. This isn’t to say one should avoid the SW200-1, but it is advisable to avoid aggressively or excessively hand-winding your SW200-1 watches as much as possible. Aggressive or excessive force is subjective, but what is generally not as subjective is the function of the automatic winding unit, which delivers a more consistent and regulated dose of energy to the ratchet wheel. Hence, the suggestion to minimize manual (and unregulated) winding of the SW200-1.
What is it?
The gold tone ratchet wheel with 63 teeth is located above the mainspring barrel. This wheel is attached to the barrel’s arbor via a single screw. It is responsible for transferring energy to wind/coil the mainspring. The energy is stored (power reserve) and released (time keeping). The stored energy is a result of either manually winding the movement via the crown, or from the spinning of the rotor on the automatic wind unit.
How to diagnose a broken ratchet wheel?
The easiest way to tell that teeth have been sheared or stripped from the ratchet wheel is by visually examining it. You may also feeling of slipping when manually winding the movement. Additionally, the watch will have dramatic loss of power reserve because of not being able to transfer full energy to the mainspring.
What to look for:
Ratchet wheel replacement part:
If your ratchet wheel needs replace and you want to attempt to DIY, the Sellita part number is #415. Below is what the packaging looks like for a genuine part from Sellita.
Sellita Caliber SW200-1 Drawings
Examples of the Sellita caliber SW200-1:
The image below is a chronometer grade (COSC certified) Sellita SW200-1 found in a Formex Essence watch.