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Thread: Lerebours Serial Number - Rice Writing

  1. #121

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    Re: Lerebours Serial Number - Rice Writing

    I have seen just about all possible combinations of scratched serial numbers, both on standard L et S lenses and the known UK users of their glass (Shew and Long) but the outer surfaces seem to be most common.

    There was a lot of variation in refractive indices in delivered glass blocks to lens makers. I only have knowledge from the workshop photos which were made which show shelves of glass blocks of different diameters. I don't think we have enough data to find out whether there were production series of the same Petzval/Landscape size with consecutive serial numbers. We know from Dallmeyers record that this was certainly the case with this larger volume maker who made to stock, rather than pressing customer demand.

    The concept of having a number of curve formers for all of surfaces (8 in all) to allow for variation in two types of glass sounds like a production nightmare, but our "resident experts" must explain how it could be done?

  2. #122

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    Re: Lerebours Serial Number - Rice Writing

    I know the glass would be selected for it's refractive indices. So perhaps there was a table, "for crown 1-3, use flint 7....for crown 4-6, use flint 8..." which would help them compensate and have similar curves ground. I also know that as they got closer to the final curve, they'd finish it by using different instruments. So each lens pair would be tested, ground some more, tested again. But that kind of blows my theory that it as for "during production", because they'd grind off the numbers if they had to do another pass. But it could be to keep them together afterwards, when getting installed in the brass. And it indicates to the mounters that the grind was complete. Just making educated guesses.
    Last edited by goamules; 23-May-2019 at 06:14.

  3. #123

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    Re: Lerebours Serial Number - Rice Writing

    I believe the serial numbers were only there to keep a set together for assembly in a barrel. It is the combination of the different focal lengths that determines the ultimate focal length of the assembly. So there is some variation allowed from cell to cell as it is the combination of both cells that sets it in the end.

    I'm with Garrett that mixing and matching of crown and flint was most likely a consideration as not doing it will affect FL significantly requiring intervention at more levels than necessary.

    Serial production was so much more efficient as you didn't have to constantly change tooling. Dallmeyer was definitely one of them.
    Quote Originally Posted by Steven Tribe View Post

    The concept of having a number of curve formers for all of surfaces (8 in all) to allow for variation in two types of glass sounds like a production nightmare, but our "resident experts" must explain how it could be done?
    Cheers,

  4. #124

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    Re: Lerebours Serial Number - Rice Writing

    Quote Originally Posted by goamules View Post

    So that begs a question: if a Lerebours has the scratched serial on one lens, is it always on the other? My number 5038 does. I'll have to pull out my other to see.
    All mine have two serial numbers, one of them has three serial numbers.

    Cheers,

  5. #125

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    Re: Lerebours Serial Number - Rice Writing

    If I had seen this item on ebay in march.
    If I had bid and won it.

    - What would I have found on the two lenses?

    The superb stereo set has just a single serial number on one lens.
    Would both lenses have identical scratched serial numbers? If so, would there be extra information to prevent mixing up matched pairs of cells?
    Attached Thumbnails Attached Thumbnails image.jpeg  

  6. #126

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    Re: Lerebours Serial Number - Rice Writing

    Quote Originally Posted by Steven Tribe View Post
    If I had seen this item on ebay in march.
    If I had bid and won it.

    - What would I have found on the two lenses?

    The superb stereo set has just a single serial number on one lens.
    Would both lenses have identical scratched serial numbers? If so, would there be extra information to prevent mixing up matched pairs of cells?
    I expect each lens to have a different serial number in this case like other stereoscopic lenses I've seen.

    Cheers,

  7. #127

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    Re: Lerebours Serial Number - Rice Writing

    Serial 4602, half plate Petzval, no WHS, rice writing on all three lenses but have not been able to remove the lenses out of the cells. Solid jam, may be later. There's writing visible on the front achromat but mostly smudged and not readable without disassembly.

    Cheers,

  8. #128

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    Re: Lerebours Serial Number - Rice Writing

    If you can read a date on the edge that would be great. So many lerebours have the serial numbers, but no way to tie them to a date.

  9. #129

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    Re: Lerebours Serial Number - Rice Writing

    Serial #10173,

    Large (81mm diameter lenses) Petzval, no SRC (none expected with this serial number).

    Front achromat seems to be re-glued a few times. Pencil marks all smeared out.

    Rear negative lens not removable as the lens cell was slightly burnished at some point.

    No WHS, no cup, restrictor still in place, beautiful specimen.

  10. #130

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    Re: Lerebours Serial Number - Rice Writing

    Sorry - a bit late - but I have now added 10173 to the list. This is still on page 7 - posting no. 63!

    It shows L et S were not very interested in WHS, even very late in their production.
    Some lenses have been seen with scratched lens serial numbers later than 10173.
    And 7442 - a large Petzval totally complete and original - has been added.
    Last edited by Steven Tribe; 4-Oct-2019 at 04:08. Reason: addition tp the list

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