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Discussion Starter #1
Hi Folks,
Sorry it's another accuracy thread, but being new to the world of COSC spec watches, I'd like some advice?

I have a 2 year old 'Bond' SMP, which I bought (used) a few months ago.
Initially it was running slow, so I sent it back to Bienne under warranty.

Now the rate over a day is generally pretty good, but:
i) When left face-up, it gains about 10s in 24 hours.
ii) When left crown-up, it looses about 8s in 24 hours.
...So by leaving it face-up over night, it keeps reasonable time, however...
iii) Just occasionally, even leaving it face-up over night, it will loose 8s in a day for no discernable reason.

Now is this what I should expect, or is there something not quite right here? I'm not too fussed about the timekeeping at present, but if this isn't normal behavour, I'd sooner get it fixed under warranty.
(My current comparison is a Citizen automatic dive watch which I have regualted to +3s per day - and this is less sensitive to position than the SMP).

Any help appreciated....
 

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If you read the COSC spec you will see that your watch is not meeting it. Presumably you have fully wound the watch before your accuracy testing?
 

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Also I would have thought the COSC certificate is only applicable at the time of certification, if your watch has previously been back for servicing / adjustment then the certification or COSC 'stamp' would be void....:-s
 

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It sounds like, in general, your watch is at least running consistently (dial up +10, crown up -8), if not entirely accurately. The good news is, if it's running consistently, it should be easier to have it adjusted to better accuracy.

One of the tricky things about checking and comparing accuracy, is that all variables must be consistent. There has to be some factor that is affecting the accuracy on the unusual times that it's dial up -8. Is it possible that you simply didn't wind the watch or wound it at a different time than normal?

eric
 

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A chronometer certification does not become "void". It is like a college diploma; you always have it. However, this does not mean that a "chronometer certified" watch can be expected keep time within the standard at all points in its life.

By the way, with proper service, a chronometer-certified watch will still keep chronometer-accurate time.

Omega actually promises somewhat better accuracy for their chronometer-certified watches than the chronometer spec. From the Omega Instruction Manual:

"To earn the title of chronometer, the mechanical move-
ment’s average daily variation in rate must be between
–4/+6 seconds per day, or a precision of 99.99%, the
highest precision attainable by a mechanical movement."

"A qualified Omega watchmaker can adjust the precision of
a watch to within the Omega tolerances, which are from
-1 to +6 seconds per day."

This is what the poster should expect if the watch was sent for service in Bienne.
 

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Discussion Starter #6
Thanks for the replies.
I can't vouch that everything (temp, level of winding, etc.) has been consistent every day. What is consistent is that I wear the watch all day (so should be pretty-well wound in the evening) - I don't manually wind it at all. It also runs fast overnight whilst not being worn, so is probably not related to the power reserve - which would be at a low in the morning.

Since the COSC standard is an average of rates in different positions I didn't know whether the behaviour I see was acceptable within spec - it sounds like it's not.

Finally as for consistency - it is generally consistent, but just occasionally looses 8-10s in a day - which is what has me most concerned.

I guess that a watch should keep good time in day to day use without getting obsessed with the correct orientation overnight....
 

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My Seamaster Pro Chrono has always run about 7 sec slow / day since I got it. I make an adjustment about once a week and not worry about it. I suppose I could have it regulated and adjusted. But, then I'd have to have it cleaned, and then might as well have the bracelet fixed, and the entire watch and bracelet refinished.

Why bother - by the time I end up doing all of this, I might as well sell the one I have with all of its imperfections and just buy a slightly used one from somebody. Afterall, it's an Omega Seamaster Chrono - there are plenty of good used ones out there.
 
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