Tissot 28.5-1 accepted accuracy

boobconsultant

for me after service, I’d be happy if it’s around +-20 sec/day and stable, thrilled if it’s consistently near +-10 sec/day. I’d push back if it’s still wandering around a minute a day unless the watch has known wear issues

Dan S

Accuracy is a subtle concept. Watches run at different rates in different positions (positional variation) and when the mainspring is wound in different amounts (isochronism). Most likely, this movement was never meant to have extremely small positional variation or excellent isochronism, it's not a chronometer grade movement and not adjusted. If you test it in 6 different positions, at full-wind and 24 hours after winding, you will likely get a pretty wide range of rates. Thus, average timekeeping on the wrist will vary from person to person, depending on use, especially for an auto-winding watch. Are you sitting? Typing? Walking? Standing? Leaving the watch dial-up on a table? How much are you moving your wrist?

I think it would be a reasonable goal to get the watch to be within 15-30 seconds a day when used in a consistent way. After the watch is serviced, I'd suggest winding it fully (e.g. 30 turns of the crown) manually before wearing it. Then wear it normally for a few days and keep tracking of the variation each day. If you are finding a fairly consistent discrepancy per day, then you can ask the watchmaker to adjust it to run a little slower/faster on average. However, if the variation is fluctuating a lot from day to day, that's going to be harder to deal with.