General question about C.O.S.C. watches

Thread: General question about C.O.S.C. watches

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  1. #1
    Member jhowton's Avatar
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    General question about C.O.S.C. watches

    I understand the meaning of the C.O.S.C. certification, the five position adjustment and the +6/-4 secs/day accuracy. My question is that for a non-certified watch with say an ETA 7750 movement, is it reasonable to expect that it can be regulated to within C.O.S.C. specs (even though it might not have been at the factory) or are the movements modified further by the manufacturers if they are destined for certification? I guess more simply put, can a good quality non-C.O.S.C. movement be regulated to within C.O.S.C. specifications?

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    Member Tragic's Avatar
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    Re: General question about C.O.S.C. watches

    I don't know what grade mvmnt. my 2836 Damasko DA36 uses but it's just dead on accurate.
    It's much closer than my cosc Seadweller or Seamaster.
    "Time is the school in which we learn. Time is the fire in which we burn."

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    Member Ray MacDonald's Avatar
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    Re: General question about C.O.S.C. watches

    Remember the difference between adjustment and regulation. Regulation just makes the watch generally run faster or slower. If it's off on positional error it won't meet COSC standards. Adjustment means it is worked on at the factory and timed to be consistent in the various positions, and only then regulated.
    Regulation works on average, and adjustment for deviation from average. Both are important for COSC (which only apply when the watch leaves the factory anyway.)

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    Re: General question about C.O.S.C. watches

    I don't know if any of my watches would pass a COSC test. I'm not about to remove the movement from it's case, remove the rotor and hand wind it every 24 hours to check how it runs in various positions. However, all of my automatics are within a few seconds of keeping perfect time when I wear them. There's also very little positional differences, actually much less than I would like. With my manual wind watches I can usually set them down at night to gain or loose a few seconds as needed, but my automatics seem to run pretty much the same regardless of position.

    I suspect that if a movement is running properly and is regulated it should keep time to within the -4/+6 COSC specs. There's more to those specs than those two numbers, but all I care about is that it keeps good time when I'm wearing a watch.

  6. #5
    Member lysanderxiii's Avatar
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    Re: General question about C.O.S.C. watches

    Quote Originally Posted by jhowton View Post
    I understand the meaning of the C.O.S.C. certification, the five position adjustment and the +6/-4 secs/day accuracy. My question is that for a non-certified watch with say an ETA 7750 movement, is it reasonable to expect that it can be regulated to within C.O.S.C. specs (even though it might not have been at the factory) or are the movements modified further by the manufacturers if they are destined for certification? I guess more simply put, can a good quality non-C.O.S.C. movement be regulated to within C.O.S.C. specifications?
    Yes, any good high quality movement (such as an ETA Top Grade) can be adjusted to meet COSC standards.

    COSC just examines the movement, and issues a certificate if it passes, they do not adjust, modify or do anything to the movement.

    (You may not have such luck with a Standard or Elabore grade.)

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    Member jhowton's Avatar
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    Re: General question about C.O.S.C. watches

    Thanks guys.

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    Member GavH's Avatar
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    Re: General question about C.O.S.C. watches

    I can confirm that having tested my meagre collection against the UK Atomic Clock very recently, my Omega Speedmaster Professional (non-COSC) is more accurate than my Omega PO (Certified Chronometer). Thus it must be possible as has been said for any high-end movement to be capable of running to within COSC spec. In the case of the Speedy Pro, it is well renowned for running to within COSC specs. I have no idea why Omega don't have the c.186x movements COSC certified before they put them in the cases. Must be historical?
    Current Pieces:
    Omega Seamaster Planet Ocean 2201.51 (Black Bezel/Orange Nos)
    Omega Speedmaster Professional 3570.50
    Omega Seamaster Professional 'Electric Blue' 2055.80
    Seiko Orange Monster
    CWC British Army 1997 issue 'G10'
    Garmin Forerunner 405

    The nice ones that came and went:
    Omega WWW CK2444
    Ollech & Wajs ID-3077 (Orange)
    Suunto Vector (Yellow, +ive face)
    Suunto Core (Black/Orange)

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    Re: General question about C.O.S.C. watches

    My 7S36 and one of my 7s26b movements (both $100-200 watches) are generally +1-4 seconds a day. Once in a while, though, especially if allowed to wind down, they'll be +15-20 sec/day, but as long as they're worn, they're very accurate.

    The "elabored" ETA 2824-2 movement in my Hamilton Khaki Field Automatic (bought new online for $243) is +2-6 seconds, usually on the lower end of that.

    The two COSC movements in my Rolexes are +2 and +4 sec/day, with very little (if any) variation. I think that's what COSC means-- good accuracy w/ little variation. They might not be as accurate as my other watches on a given day, but they're far more consistent and by the end of the month, they'll be closer to the real time than the others.
    My Collection:
    Casio G-Shock GW-M5600-1CR
    Seiko Kinetic Auto Relay 5J21-0A10
    Seiko SKX031
    Seiko blue Atlas SKZ209
    Seiko Spirit GMT SBQJ015
    Seiko SKX781 Orange Monster
    Seiko SCVF001 titanium diver
    Seiko SBDX001 Marinemaster 300M
    Grand Seiko GMT SBGM027
    Hamilton Khaki Field Automatic
    Rolex Explorer I 114270
    Rolex Submariner-date 16610
    Omega Speedmaster Professional 3570.50
    Stowa Flieger Original 1
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    Stowa Marine 6425
    Tudor Pelagos 1
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  10. #9

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    Re: General question about C.O.S.C. watches

    Quote Originally Posted by jhowton View Post
    I understand the meaning of the C.O.S.C. certification, the five position adjustment and the +6/-4 secs/day accuracy. My question is that for a non-certified watch with say an ETA 7750 movement, is it reasonable to expect that it can be regulated to within C.O.S.C. specs (even though it might not have been at the factory) or are the movements modified further by the manufacturers if they are destined for certification? I guess more simply put, can a good quality non-C.O.S.C. movement be regulated to within C.O.S.C. specifications?
    Yes, it is reasonable to expect that and yes they can. My Serket Reef Diver 2.0 has the Sellita SW200 which ran -1 per day straight out of the box, non COSC, and the watchmaker I took it to said he could have it regulated/adjusted to run at any rate I want. All it takes is a competent watchmaker my friend.

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    Re: General question about C.O.S.C. watches

    I know this may be here somewhere but since this COSC thread is closest to the top, anybody care to elaborate on the 5 positions that they regulate at?

    I also heard that the GRAND SEIKO regulates at a SIXTH position- what is it?

    Yes, my Seikos have ran within COSC spec during regular wearing- but I doubt if they can survive the 5 positions test- let alone Six.

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