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Old 4 March 2019, 03:27 AM   #1
Tork
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Cosc

Was wondering... with COSC being -4/+6, why is running faster at +6 a greater margin of accuracy when compared to running slower?
Thanks...
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Old 4 March 2019, 04:58 AM   #2
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The bias towards gaining is largely based on watch wearers being more tolerant towards a watch gaining over losing.

The target range there is 10s and that is the ‘real’ characteristic of a chronometer - isochronism within 10s. The average rate -4+6 is often quoted but is it really the impressive number. A watch with a delta of 100 could still be regulated to average out at +-0, but would in no way be meeting chronometer specs.

Hope that helps and I’ve not made it more confusing.
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Old 4 March 2019, 09:46 AM   #3
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Quote:
Originally Posted by Tork View Post
Was wondering... with COSC being -4/+6, why is running faster at +6 a greater margin of accuracy when compared to running slower?
Thanks...
You are misapplying the COSC "standard".

COSC is a torture test, and during one phase, the movement must stay within a 10 second swing of -4/+6 from a set base time in order to pass the test.

Too many think that "within COSC" means that if your watch runs at +6 daily it is "within", but that is way too simplistic.
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Old 8 March 2019, 01:48 PM   #4
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Imagine it's just a preferential bias to have the watch run a little fast overall. Hacking the second hand to reset is a lot easier than dealing with the minute hand, then waiting on the second hand and so on.
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Old 8 March 2019, 02:50 PM   #5
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Quote:
Originally Posted by Tork View Post
Was wondering... with COSC being -4/+6, why is running faster at +6 a greater margin of accuracy when compared to running slower?

Thanks...


Rolex fixed that - now it’s -2/+2.

They say “take that COSC”


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Old 8 March 2019, 10:05 PM   #6
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Rolex fixed that - now it’s -2/+2.

They say “take that COSC”


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Even after testing on a machine to this new-2+2 spec ,its possible it could vary while on the wrist in he real world.Just like when the test car fuel consumption in a controlled environment,its doubtful if the driver will get the exact same miles per gallon.Just to many variables like traffic, how heavy foot on the gas pedal,gear changing etc, well its like that with watch movements while on the wrist.
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Old 8 March 2019, 10:30 PM   #7
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Even after testing on a machine to this new-2+2 spec ,its possible it could vary while on the wrist in he real world.Just like when the test car fuel consumption in a controlled environment,its doubtful if the driver will get the exact same miles per gallon.Just to many variables like traffic, how heavy foot on the gas pedal,gear changing etc, well its like that with watch movements while on the wrist.


All true Peter. No mechanical watch in real world will perform as a cased movement on the bench. If one wants perfection, choose a quartz model.

As you prolly know, I was being light-hearted in my reply. I believe there is no way for anyone to know the answer to the OP’s original question.

Can you share any knowledge on the “why” of COSC limits?

Many have opined on the range being 10 seconds (-4/+6).

But why wasn’t it set at -5/+5?
Or -6/+4?

Ultimate Rolex WatchTech trivia round 2...


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Old 9 March 2019, 12:03 AM   #8
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Originally Posted by 77T View Post
All true Peter. No mechanical watch in real world will perform as a cased movement on the bench. If one wants perfection, choose a quartz model.

As you prolly know, I was being light-hearted in my reply. I believe there is no way for anyone to know the answer to the OP’s original question.

Can you share any knowledge on the “why” of COSC limits?

Many have opined on the range being 10 seconds (-4/+6).

But why wasn’t it set at -5/+5?
Or -6/+4?

Ultimate Rolex WatchTech trivia round 2...


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First you must understand why the Swiss COSC was founded and set specification agreed on by all the main Swiss manufactures at average -4+6 seconds,now before the Swiss COSC was started in 1973 they used to have Observatory testing competitions and they were to much higher standard than today's Swiss COSC. Now during the entire 23 years of testing these Observatory tests,just 5093 wristwatches were submitted for certification, and only 3253 were passed, about 64%,now today around 96% of all the millions of movements submitted pass the COSC test first time thats a huge difference because its a much lower standard than before. Now truth be told today with careful regulation most any movement could pass today's watered down COSC test.The European din standard and the Japanese standard was to a higher standard the the Swiss COSC around the same spec as the new Rolex and Omega -2+2 spec.Now back in the 1960-70s just a few manufacturers participated in these Observatory testing competitions, and only Omega and Patek did so every year. The other main brands. were: Rolex, Zenith, Longines, Movado, Vacheron & Constantin, Ulysse Nardin, Cyma and Favre-Leuba, along with numerous independent professional watchmakers.

That was until watches like the Seiko Grand come on the scene and started to wipe the floor with the Swiss mechanical watch industry.Now in those days only 2 brands in the + 23 years of the competitions submitted movements of only serial production for retail sale(Seiko and GP).All others were specially made movements just for the competition test and not then for retail sale.

Now Seiko first entered the competition,with other watches from all over the world,including most of the Swiss high end brands.But then for a much higher standard than today's COSC,the Astronomical Observatory Authorisation Chronometer Standard (+/- 2/3 seconds over 48 hours) Out of many watches submitted only two passed this test a Seiko Grand just a production model, and Giraud Peregaux this time a specially build for the test model.And in the late 1960s there were only two companies, who could sell watches, passed astronomical observatory authorisation Chronometer in those days,just Seiko and Giraud Peregaux.As the Japanese had dominated the tests in the very late 1960s and the two preceding events the early into the 1970s.So in 1972 many of Swiss watch manufacturers demanded the end of the observatory competitions,and it was ended in 1973,now thats when the Swiss COSC was founded but run by the Swiss but for the Swiss brands only.Because of the high volume of movements tested by Rolex at the COSC Rolex has there own machine there to test there movements and Rolex is one of the biggest payee to the Swiss COSC.
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All posts are my own opinion and my opinion only.

"The clock of life is wound but once, and no man has the power to tell just when the hands will stop. Now is the only time you actually own the time, Place no faith in time, for the clock may soon be still for ever."
Good Judgement comes from experience,experience comes from Bad Judgement,.Buy quality, cry once; buy cheap, cry again and again.

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Old 9 March 2019, 12:41 AM   #9
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Quote:
Originally Posted by padi56 View Post
First you must understand why the Swiss COSC was founded and set specification agreed on by all the main Swiss manufactures at average -4+6 seconds,now before the Swiss COSC was started in 1973 they used to have Observatory testing competitions and they were to much higher standard than today's Swiss COSC. Now during the entire 23 years of testing these Observatory tests,just 5093 wristwatches were submitted for certification, and only 3253 were passed, about 64%,now today around 96% of all the millions of movements submitted pass the COSC test first time thats a huge difference because its a much lower standard than before. Now truth be told today with careful regulation most any movement could pass today's watered down COSC test.The European din standard and the Japanese standard was to a higher standard the the Swiss COSC around the same spec as the new Rolex and Omega -2+2 spec.Now back in the 1960-70s just a few manufacturers participated in these Observatory testing competitions, and only Omega and Patek did so every year. The other main brands. were: Rolex, Zenith, Longines, Movado, Vacheron & Constantin, Ulysse Nardin, Cyma and Favre-Leuba, along with numerous independent professional watchmakers.

That was until watches like the Seiko Grand come on the scene and started to wipe the floor with the Swiss mechanical watch industry.Now in those days only 2 brands in the + 23 years of the competitions submitted movements of only serial production for retail sale(Seiko and GP).All others were specially made movements just for the competition test and not then for retail sale.

Now Seiko first entered the competition,with other watches from all over the world,including most of the Swiss high end brands.But then for a much higher standard than today's COSC,the Astronomical Observatory Authorisation Chronometer Standard (+/- 2/3 seconds over 48 hours) Out of many watches submitted only two passed this test a Seiko Grand just a production model, and Giraud Peregaux this time a specially build for the test model.And in the late 1960s there were only two companies, who could sell watches, passed astronomical observatory authorisation Chronometer in those days,just Seiko and Giraud Peregaux.As the Japanese had dominated the tests in the very late 1960s and the two preceding events the early into the 1970s.So in 1972 many of Swiss watch manufacturers demanded the end of the observatory competitions,and it was ended in 1973,now thats when the Swiss COSC was founded but run by the Swiss but for the Swiss brands only.Because of the high volume of movements tested by Rolex at the COSC Rolex has there own machine there to test there movements and Rolex is one of the biggest payee to the Swiss COSC.


Yes, yes and yes...

But any idea why the delegates used -4/+6?

And not -5/+5 or -6/+4?


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