|Based On||ETA/Valjoux 7750|
|Movement Type||Automatic, self-winding mechanical, chronograph|
|Vibrations Per Hour||28,800 (4 Hz) – early models were 21,600
||200 – 310 degrees
||56 – 62 hours
|Fine Timing Device?
|Chronograph System||Three-plane cam style|
|Rotor||Ball bearing system|
||Nickel gilt or Glucydur (depending on grade)|
||2mm x 1.2mm x 0.25mm + 3 x 0.18mm|
||6 (may depend on variation)|
|Features||Central hours; central minutes; central chronograph seconds; small running seconds at 9:00; 30 minutes chronograph counter at 12:00 (also possible as a 15 minutes chrono counter); 12 hours chronograph counter at 6:00; day/date at 3:00 (may be in a different location depending on the dial design of the watch)|
|Country of Manufacture||Switzerland, Swiss made|
|Known Models||(Too many to list! Please add your watch to the comments below…)|
The Sellita caliber SW500 is a 6-9-12 layout automatic chronograph movement based on the popular ETA/Valjoux 7750 framework. It is what is referred to as an “ETA clone” movement. This caliber was introduced as a Swiss made competitor to the 7750 and has been on the market since at least September 2012. Official tech docs have been updated as recently as April 2021. You may also see this caliber written as SW 500 or SW-500, however, Sellita officially calls it “SW500” without the space or hyphen.
In Sellita’s own words:
“Renowned for its legendary robustness, the SW500 is the quintessential Swiss automatic chronograph. The SW500 is characterised by its integrated chronograph mechanism (visible through an open caseback) and its multiple functions, which include a 30 minutes counter, a 12 hours counter as well as date and day display.”
Some of the topics covered in this caliber listing:
Sellita SW500 Grades:
There are 3 grades of SW500. The grade determines the finish, the positions the movement was tested in at the factory, the expected average accuracy, and the material/finish used for the balance wheel.
Tested in 3 positions; average accuracy of +/- 5 seconds per day with a max deviation of 20 sec/day; nickel gilt balance wheel.
Tested in 5 positions; average accuracy of +/- 4 seconds per day with a max deviation of 15 sec/day; Glucydur balance wheel.
Tested in 5 positions; COSC accuracy spec; Glucydur balance wheel.
Learn more about Sellita movement grades here
Typically the finishing of a movement corresponds with the grade, but it does not seem to be entirely set in stone. The guide below can help you figure out which finishing option the brand of your watch decided to use. Please comment below with your brand specific insights.
In addition to different grades, the SW500 family of chronograph movements has various configurations available. Most watch brands will simply write “SW500” in their specs list as to not be overly complicated for the consumer (we all know that some won’t even tell you that much), but the list below can help you determine if your watch is a variant of the SW500. If so, please comment below.
The different versions of the SW500 are as follows, with only the main differences being listed:
- SW500 a – Base chronograph caliber; 6-9-12 subdials; day/date at 3:00
- SW500 b – Date only
- SW500 c – No date
- SW500 BV a – 6-12 layout; day/date
- SW500 BV b – 6-12 layout; date only
- SW500 BV c -6-12 layout; no date
- SW500 MP a -12 subdial only; date at 6:00; monopusher (button for the chronograph at 2:00)
- SW500 MP b – 9-12 layout; date at 3:00; monopusher (button for the chronograph at 2:00)
- SW500 MP c – 9 subdial only; date at 3:00, monopusher (button for the chronograph at 2:00)
- SW500 MPC a – 12 subdial only; date at 6:00; monopusher (chronograph pusher integrated into the crown)
- SW500 MPC b – 6-12 layout; date at 6:00; monopusher (chronograph pusher integrated into the crown)
- SW500 MPC b – 9 subdial only; date at 3:00; monopusher (chronograph pusher integrated into the crown)
BV stands for bi-compax vertical. MP stands for monopusher. MPC stands for monopusher crown. There are also manual wind versions of the SW500 designated as SW500 M.
Improvements over the 7750:
Although the 7750 is a much loved movement in the watch industry, every watch with a 7750 has a potential to face mechanical issues when the user adjusts the day/date between 8pm and 2am. To the watch enthusiasts new to the 7750, this can take some getting used to, especially since calendar correction mode is the first click when pulling out the crown for time/date setting. It’s common for a user to pull out the crown, adjust the date, then the time… but doing so within the no-set span can easily cause the dreaded day/date flipping at 5am phenomenon which requires service to correct.
The evolution of the SW500, as issued via technical communication by Sellita on August 27, 2020, upgrades both the day and date driving wheels, as well as the intermediate setting wheel, to help avoid the issues discussed above. Sellita describes the new parts as follows:
“The calendar driving wheels and the intermediate setting wheel have been modified to ensure that the quick setting of the date and day can be operated any time.” –source
Editor’s note: This is rather new and I have not tested it, nor am I inclined to. Too many bad experiences with 7750 time/calendar setting. If you happen to have more information about being able to set newer SW500 based watches at any time, then please comment below.
On December 17, 2020, Sellita issued another evolution to the SW500 which increases power reserve from the the standard 48 hours up to 62 hours. This is possible thanks to a new and improved barrel design.
“In order to increase the power reserve of the SW5XX movement family, we have developed a barrel with better performance. This new barrel, called “RDM+”, is recognizable by its diameter of the axis.” –source
What they mean by it being recognizable by its diameter is that despite the new barrel offering more running time, it is actually smaller in diameter: new 1.810mm vs old 1.985mm. It sort of makes you wonder why they couldn’t keep the same size diameter and squeeze more coils of the spring into the barrel for a few extra hours of PR.
- Old barrel part number: 020.010.00025
- New barrel part number: 020.010.00110
Note that Sellita oil charts state that it is not advisable to clean the barrel during a service.
How to tell if you watch has the new barrel?
Aside from noticing longer 62 hours power reserve, another way to tell if your watch was produced with the higher capacity barrel is by the date code on the movement. This is located near the caliber number, below the balance wheel. The new barrel part was implemented as of date code DM21.1/XYZ.
Editor’s comments: Thank you Sellita for being transparent with stuff like this!
SW500 Chronograph Operating Instructions:
Button sequence: Top, top, bottom.
- Top button: Start/Stop
- Bottom button: Reset
Chronograph Hand Lining Up:
Unlike quartz powered chronograph movements, mechanical watches do not have the luxury of using a reset sequence to get the chronograph hand to line up to 12:00. If your caliber SW500 powered watch has a hand that is not lining up, it could be a mechanical problem and should be inspected by a professional watchmaker. Your watch may need serviced or the hand might need to be reinstalled.
Crown/stem removal on the SW500:
What hand setting position should the crown be in to remove the stem? Hand setting position (pull the crown out two clicks).
What size screw driver should be used to press the detent button? Use a 1mm watchmaker’s screw driver and do not press down too hard.
SW500 Dial feet location: