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  1. #11
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    Re: Longines Prima pocket watch 19.71N

    hello
    hope this help.
    https://www.balancestaffs.com/longines.php?caliber=
    regards enrico
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  2. #12
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    Re: Longines Prima pocket watch 19.71N

    Wow.
    Yes, thank you. Finally. The spare parts catalogue.
    Thank you for the links 707mm2!!!!
    And Enrico!!

    The balance staff is unique to the 19.73N (505, 250). But is the balance wheel also unique, or did Longines use the same wheel for which calibers?

  3. #13
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    Re: Longines Prima pocket watch 19.71N

    Hi,

    Actually your balance wheel may also be unique... Aside from the 19.73N, I've never seen any 19 lignes Longines movement with a nickel balance like yours. Even if they exist, they must be too rare to look for them as replacement source. I believe Longines used nickel balances only on some special watches in the 1930s, mostly chronographs like yours and the 13.33, or military watches like the 15.26. There may have been some military 19.95 with nickel balance but it's an entirely different beast. The vast majority still used bi-metallic balances, and from the late 1930s came beryllium alloys like glucydur that definitely got out nickel balances from Longines' production.
    Last edited by 707mm2; 1 Week Ago at 01:34.

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  5. #14
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    Re: Longines Prima pocket watch 19.71N

    Thank you. And again please excuse my diversion, shall I move this topic back here?
    I found a replacement from a 19.73N from around 1910. The double face model was produced with 19.73 and 19.73N – see this model in the Longines museum. And see that thread for more details. I'm attaching a microscope image of this older balance.
    Attached Images Attached Images


  6. #15
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    Re: Longines Prima pocket watch 19.71N

    I love diversions. After all, we're here to talk as long as we want about watches ;)

    Be aware that even if some Longines calibers bears the same reference, like 19.73N in your case, they still may have slightly different parts than the one exact model you have. It's because Longines implemented different complications (different chronograph mechanisms in your case) for the same base caliber. Because some complications may require more or less power from the mainspring, it's quite possible the donor balance does not have the same weight, or the hairspring the same strength, as your first movement. And even if they have the same complication, its service history may have included some alterations to the original adjustments. In consequence, there might be a need to re-poising the balance, and that's gonna take time to get it properly working. May I ask what was wrong with the original balance wheel ? While the staff is a relatively frequent replacement, it's quite rare to have to replace the whole balance.

    I hope it's just an optical illusion because it's out of focus but the terminal curve of the hairspring seems wrongly bent near the stud ?
    Last edited by 707mm2; 1 Week Ago at 04:08.
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  7. #16
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    Re: Longines Prima pocket watch 19.71N

    Thank you

    I am no watchmaker, I inherited this Silver Shadow of a chronograph and have been trying to have it repaired – and understand it – since 2016. I still have 1001 questions
    I still find it fascinating and I still think the 19.73N might be one of the finest modern industrial calibers.

    The watch lay forgotten in a drawer. After a fall that dinged the tachometer face and broke the glass, the balance was badly repaired in the late 50s. In 2016, a standard Rhonda replacement (still is easy to find) did not fit because of that. More details in this thread I started. And this is a link to a documentary of a second repair (see that thread for details of the first).

    Now the same watchmaker accepted to replace the balance. You are right about the hairspring. He righted it. However I fear he may have failed to notice the lower pivot is bent (or chose to leave it alone) and he compensated for a 1,5 tenths difference in height by setting the stone higher. Or so I understand. I hope I am wrong.

    The Longines brochures came a bit late but they are great! I haven't yet had time to take a good look (been busy with the next heir of the watch, age 31/2 but as far as I looked the Materials sheet shows one balance wheel for the 19.73N, which is also unique (in more ways than one). How many variants of the 19.73N(ew) were there? in one of the sales brochures, Longines says: “Longines parts are so standardized that they are entirely interchangeable.”

    My double face was made around 1928. I read there also was a 19.73K (whatever that means) I've never seen. I have a lot of 19.73N photos in normal watches, I only know of four double faces.

  8. #17
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    Re: Longines Prima pocket watch 19.71N

    “Longines parts are so standardized that they are entirely interchangeable.”
    Longines were quite proud of their interchangeability, they were among the very first manufactures to offer a high degree of standardization, but it was only true for a given model. The problem with Longines is that they certainly made more different calibers, each with their own variants, than any other companies, especially in the early 20th century. Taking your own example, the 19.73N, there was the basic chronograph version, a rattrapante version, double faced version, many variations too in the regulator (it could be a simple straight one, or with a snail cam, or going down to a cut out in the case like yours). Finish too could vary, most 19.73 had nicely polished steel parts but some had a higher "mirror" grade finish with bevels, the bridges could be gilded like yours or with nickel plating and geneva stripes, engravings on the balance cock changed too over the years...
    This continued well after WWII, when Longines used for example different types of shock protection on the balance, meaning you had different balance staffs depending on the caliber AND type of anti-shock device. A simple and popular calibre like the 12.68Z had so many variations too, wether it had sub or central second, chronograph, date, chronometer quality, different bridge shapes, and of course different finish.
    Again, I can't think of any other brand with such a extremely wide range of different calibers, variations and finish.
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  9. #18
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    Re: Longines Prima pocket watch 19.71N

    However, you assumed balances might differ between complications etc. The Longines spares catalogue only lists one (unique) balance for the 19.73N caliber, the only unique caliber, it seems…

    The topic has become academic, because the watchmaker could use a 19.73N balance with a bent pin – he somehow rectified or straightened it. I thought this is not possible, but he says it is working perfectly. I haven't yet received my double face back, but I sent him the spares-list.

    Did you see have a look at his documentary of the first part of the repair? I'm interested in any comments!

    Thank you again!

  10. #19
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    Re: Longines Prima pocket watch 19.71N

    you assumed balances might differ between complications etc. The Longines spares catalogue only lists one (unique) balance for the 19.73N caliber, the only unique caliber, it seems…
    But there is actually more than one balance ! If you make a quick search about the 19.73N, you will notice at least three different balances : a cut bi-metallic one, a plain nickel one like yours and a beryllium alloy/glucydur one for later models. I can't find it, but I clearly remember seeing another variation with an extra small balance to get higher frequencies. But I admit that wether the 19.73N had a simple chronograph or a rattrapante or double face complication induced slightly different balance is just an assumption, only based on my experience that some complications may require more or less power, I'm not expert enough if it's actually the case for the 19.73N family. Does your catalogues lists parts for the three usual complications of the 19.73N (simple chrono, rattrapante and double face) or just one ?
    What I know for a fact, is that Longines does not always list all of the actual parts in their catalogues... One simple example, some Longines 30L were made with a breguet hairspring (I actually own one of those), but the on 30L parts list you'll only find references for the flat spiral version.
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  11. #20
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    Re: Longines Prima pocket watch 19.71N

    some examples
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    regards enrico
    Last edited by eri231; 1 Week Ago at 20:00.
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