I had assumed this would be a common topic of conversation but my searches have not come up with any topics on the subject.
I have had a grand total of 2 mechanical watches. The first (20 ish years ago) was a heuer cerera re issue that I could not really afford but it was beautiful, I did not know a mechanical could be 20 seconds a day out and it really got on my nerves, luckily the shop agreed to take it back.
in the meantime I bought some military issue seiko's but still lusted after a mechanical watch.
I decided to buy a cheap and cheerful Seiko 5 to see how I felt about having a watch that varied each day before splurging on something more expensive. I’ve been wearing it for a couple of months and initial timings suggested it was 8-10 seconds a day out. I was enjoying wearing it and decided to test it over a week and it seemed to be about 2 seconds a day out over that time. I did another test yesterday which showed it was out by 0.1 seconds a day which i feel is astonishingly good.
so now I’m in the situation where I find I like using a mechanical watch to tell the time but my head is telling me that accuracy like this is incredibly rare and when I buy a different watch I’ll have something that is nowhere near as good but costing at least ten times more.
so what I want to know is how accurate are mechanical watches over time, eg a week, a month? Would a COSC certified watch be more likely to do the same thing every day? Eg run 3ish seconds fast a day so over a week be 21 seconds out. Or would a COSC watch be more likely to be a couple of seconds slow one day, a couple fast the next day so it evens out over a week?
Im more likely to buy something like a Sinn 556 (I love tool type watches) and from what I have heard they are fairly accurate but they are in spec if they are within plus or minus 20 seconds a day so I guess that means they could be out by over 2 minutes in a week.
so basically what is reasonable time keeping of a mechanical watch over a week or month?