Omega case number question (2846-2848 4sc)

Discussion in 'Watch Repair' started by deloid, Jan 14, 2017.

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  1. deloid

    deloid Registered User
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    I'm working on an Omega Seamaster with the case number 2846-2848 4sc. Ofrei doesn't have this listed as a case number when searching for crystals. There is a crystal for 2846 that also fits 2848 but I don't know if this might be correct.

    An explanation of this case designation that is new to me would be appreciated.
     
  2. roughbarked

    roughbarked Registered User

    Dec 2, 2016
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    Where are you reading this number from?

    From Ofrei:

    Only the case number is going to get you a crystal. So open up the back case an look for the number on the inside of the case back, which is called the case number. Once you have the case number you can order a crystal. Please note that from the case number we cannot tell what color the watch is so if the crystal has a white or yellow ring you must tell us.
     
  3. deloid

    deloid Registered User
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    Roughbarked:
    The typical region of the case back.
     
  4. roughbarked

    roughbarked Registered User

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  5. deloid

    deloid Registered User
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    You probably didn't realize that your statement "Well if you believe you are doing it correctly" is condescending but I won't spend more time on that.
    I know the Omega addict page and it doesn't help me. I don't need an ID on the watch.
    As far as ordering and letting the tech/sales person find the correct part? That will work but they do make mistakes and the more important component is that I, and most, should understand and know what is being ordered. While I know Omega watches well, this 1950's case designation throws me. There must be some rationale for this unusual case designation.
     
  6. dAz57

    dAz57 Registered User

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    #6 dAz57, Jan 14, 2017
    Last edited: Jan 14, 2017
    According to my omega case reference page case no. 2846/48 uses crown # 42023 and glass is # 5140.

    On the page it's simply called a glace, no description of whether it's a mineral crystal or an armoured Plexi, when ordering you need tell the supplier the colour you want, gilt or steel


    Ok an armoured ring Plexi with yellow tension ring, if yours is steel you will have to use the old ring

    4th one down on the left
    http://www.ofrei.com/page_168.html
     
  7. Al J

    Al J Registered User

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    Not uncommon for case backs to have more than one reference inside them. I've seen as many as 4 inside one case back.

    For a stainless case, the crystal number is 063PZ5140, and the current replacement crown is 069ST42023. Crystal is acrylic of course.

    Cheers, Al
     
  8. deloid

    deloid Registered User
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    Thanks! Glad you both agree on the "glass" number :)
    Al J- Any theory as to why Omega had more than one reference number? Perhaps case backs that fit other case models? Is it generally safe (with an Omega) to say that either number would lead to the correct crystal/crown?
     
  9. roughbarked

    roughbarked Registered User

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    As stated above, if you have the correct case number from the inside of the case back, then the part number can be known. These Omegas with standard tension ring glasses, don't actually have to be fitted with an original Omega glass. any correct size ATC glass will fit, though in many cases the original tension ring may be required for the new glass to fit correctly. After all a 31.5 diameter is the same whatever brand of plexi. Of course it is desirable to be able to read the Omega symbol on the underside in the center but not entirely necessary if the original is difficult to find.
     
  10. deloid

    deloid Registered User
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    I don't agree. Many if not most generic crystals that can be used on the Omegas (that require a tension ring) do not have the step that allows for proper seating. A generic crystal may cause problems with the rotor movement.
     
  11. Al J

    Al J Registered User

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    Indeed, most Omegas with an armored crystal use a stepped tension ring, and not having it can cause problems such as the stem not lining up in the case tube (will eventually work harden the stem and cause it to break from flexure during winding/setting), and in extreme cases the rotor scraping on the case back.

    Regarding why they have more than one number, it's because case backs can be used on more than one case reference. I would not always assume they use the same crystal though, even though in this case they did as I checked both.

    Cheers, Al
     
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