Hi to everyone,

New member here from Turkey. Collecting, buying and selling vintage watches.
I acquired a Seamaster Calendar from 1958. Time-tested it and it is gaining 150 secs/day in average.
Calibre is 503. Do you think this is a reasonable inaccuracy?

 

No of course not. It likely needs a service.

 

Absolutely not.

 

Even the Omega service manual specifies +25/-30spd for their vintage calibres. A competent watchmaker can get it better than that.

 

It definitely needs a good service.
Can you share some pics?

 

No, far to high. Like a -3,5 positional evaluation, some don't care, but it's not good in the long run.

 

sticky hairspring?

 

Demagnetizing might help, but a service is most probably a good idea.

 

yep, it can be many things.