Hello, I have a Semaster 300 (watchco) with vintage 565 calibre from 1970 on rotation which started to behave strangely… First running 2 mins/day fast, then keeping perfect time, then losing 2 mins/day – all just in few weeks.

Before it was running strong for a few months and seller promised it was checked and no needed service yet.
But a week ago after wearing it I saw it was running about 2 min./day fast. I checked it with Hairspring app with ok result (like +18sec) but physically it was gaining about 2 minutes.
After few days I decided to check it again. Surprisingly it was running accurate, just 2-3sec/day so I started wearing it for a few days again.
After some days resting in a box, I picked it again and it is losing 2 mins/day now.

What can it be? Seems like the first minute it loosing (or gaining when it was running fast) already in 1 hour. Then it runs better.

 

Am I the only one who thinks a trip to a watchmaker might be in order?

 

"No needed service yet" as stated by the seller. Usually a euphemism for "It performs good enough for me". The watch is about 50 years old. Always a smart move to have such a watch checked out by a shop that has a good reputation on vintage and antique watches. Does anyone trust the seller when they are told the watch has been "professionally and thoroughly serviced"?

 

Not without proof.

 

Thanks so much! Sure I wanted to go to watchmaker right after I saw it run faster, but then when it started to show correct time I was confused. So I was thinking maybe somebody will explain this as magnetism or whatever could it be. Now I remember the day before I saw it started to run fast I was wearing it on some event standing quite close to big sound system for instance...