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Thread: Longines steel 6b/159 question

  1. #1

    Default Longines steel 6b/159 question

    I picked up this Longines on ebay last week (poorly listed, but I certainly wasn't the only person bidding on it!)

    I thought it looked like one of the steel-cased 6b/159s with a skimmed caseback - crown / dial / minute hand are all correct for this.

    Having got the watch though I'm not really sure and would appreciate any thoughts.

    It certainly looks like a steel case, the profile is different from the two alloy cased ones I have.

    Also I note that the back of each of the lugs have a sort of seam which looks similar to one that was sold on classicwatch.com a while back (see here)

    Thing is the case doesn't appear to be skimmed. I measure it as 0.58mm, which is the same as an engraved caseback that I have; I have another alloy-cased Longines 6b/159 which has a skimmed case back and that one measures 0.45mm

    Also I'm unsure about the "Staybrite" formulation which is marked on the caseback, I don't see this on foilguy's stainless 6b from this thread which I was using as a reference.

    So I guess my questions boil down to:
    - does anyone else have a "Staybrite" marked Longines 6b/159?
    - anyone else measure a skimmed caseback as thick as 0.58mm?
    - is there a possibility it's a non-issued model or indeed a civilian watch that's very similar to the 6b/159?
    - is there any info about the numbering inside the case back?

    thanks in advance for any help!

    Crispin





  2. #2

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    could it be a service replacement case back? I could imagine someone doing that -- either to civilianise it or because the original one was damaged
    "Early this year I saw ex-army watches exhibited in a showcase at a little under 4 each. A week or two later I succeeded in buying one of them for 5. Recently their price seems to have risen to 8." (George Orwell, "As I Please", Tribune, 29th November 1946)

  3. #3
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    Could ask Longines for an extract. It's not easy to find replacement casebacks for these, especially if its the stainless version which if I remember correctly is rarer.

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    Member isologue's Avatar
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    Quote Originally Posted by rodabod View Post
    Could ask Longines for an extract. It's not easy to find replacement casebacks for these, especially if its the stainless version which if I remember correctly is rarer.
    +1. What's the movement number? That might reveal more than the case.

    Regards,

    Martin (isologue)

  5. #5

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    @Revo yes, replacement case back did cross my mind (maybe an earlier one as I think Staybrite was pretty much obsolete by the 1940s)

    @ rodabod I noticed this - the three I have don't interchange, seems a bit odd - I'd have thought for production it'd have been simpler (= cheaper) to standardise these...

  6. #6
    Member Kiwi's Avatar
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    Your caseback is correct for an AM watch. I have a similarly polished example.
    21250 is the correct case model for the stainless (more correctly Firth's Staybrite) case Longines 6B/159. 656 is the unique number for the case, on later watches the 8 would be 6, a repeat of the last digit of 656 (why?) and I haven't worked out what the 10 is. An inspectors stamp perhaps?
    Weems cases are also staybrite. Marked examples of the 21250 tend to have an unusual AM serial around 10000 that doesn't have a year identifier, but fit into the 1940 sequence.
    If you email Longines customer service with the movement number they will probably confirm it was invoiced to Baume UK in early 1941. Mine is from April 1941 iirc.
    I will have a crack a measuring my caseback, but as I think it has been polished this my not help.
    Regards
    Kiwi

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    not that much that I can really add here Crispin.

    yes the case is definitely all stainless steel.

    the cracks or seams are normal and part of the manufacturing process.

    you could have ten of these watches and none of the case backs would probably interchange!

    I have also encountered similar polished case backs that don't appear to have been skimmed.

    try weighing the case backs rather than measuring..
    Last edited by dave; 03-08-2017 at 14:17. Reason: grammar.

  8. #8

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    @Kiwi great, thank you - I had a vague memory that the five digit number was a case identifier, but I was confused because foilguy's 6b (which is stainless also) has a quite different code : 22313

    Having said that, foilguy's case looks slightly different (much squarer ends to the lugs), in which case were there two steel cases?

    I noticed in Knirim that the weems Longines were also Staybrite.

    I'll mail Longines

    @ dave, many thanks I didn't think to weighing the casebacks, will try tomorrow...

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    Member trident-7's Avatar
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    I was going to say that mine doesn't have "Staybrite" but then I realised that it is actually Foilguy's old watch

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    Member Kiwi's Avatar
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    Yes 22313 is the other AM stainless case model. There are also half a dozen different model numbers for the later alloy case types that appear, in a roughly chronological order. I suspect these are all subtly different hence the lack of interchangeability.

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    Crispin, get the calipers on it. I can do the same on my three which I own. Mine aren't interchangeable either....

  12. #12

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    ok so the case backs I have measure as follows:

    alloy case, engraved = 0.58mm
    alloy case skimmed = 0.45mm
    case back for this case (so no engraving, but the right model number inside etc) = 0.58mm

    Anyone else able to measure to add to the above?

    Movement serial is 6104326 which I believe puts it 1940/41

  13. #13
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    I'll check my thicknesses, but what I actually meant was, measure the inside fitting on the caseback so that we can find the correct back for your one if you end up looking for one.

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    Member isologue's Avatar
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    Quote Originally Posted by mrjones View Post
    Movement serial is 6104326 which I believe puts it 1940/41
    Yes close to Kiwi's 1941 example I should think.

    Regards,

    Martin (isologue)

  15. #15

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    Quote Originally Posted by rodabod View Post
    I'll check my thicknesses, but what I actually meant was, measure the inside fitting on the caseback so that we can find the correct back for your one if you end up looking for one.
    sorry that makes more sense

    Ok measuring the inner lip of the case back I get 30.39mm and an outer diameter of 32.28mm

    Very grateful if anyone happens to have a correct engraved case back that they can offer.

  16. #16
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    I will get mine measured when I get a chance.

  17. #17
    Member Kiwi's Avatar
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    If it helps, my watch has case is 21250 868. The watch came to me with 12.68n movement serial 6100194, so very close to yours. Unfortunately the movement was terminal so it now has a later 12.68n.

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