Hand Written Numbers Inside lenses- What are they ?

[M_Kelly_Cinematographer]

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Hello Leica Forums,  First post. I own about a dozen R lenses, mostly pre-rom.  

I recently opened up two of my lenses for cleaning. (24mm 2.8 & 28mm 2.8 both 3-cam)   I discovered that both lenses had hand written numbering inside.  Specifically each of them had a pair of matching numbers.  One number was written on the front lens group and the same number was also written on the rear lens group.  I have attached an example from the 24mm lens.  I am guessing that these numbers were written durning manufacturing perhaps as part of the alignment and quality control process.  I am further guessing that perhaps these numbers might be part of a lens element matching refinement process, but that is just a guess.

Does anyone have more information on the function of these numbers written inside the lenses?

 

PS, I did do a little searching before I posted this question, but searching for the word  "number"  returns a lot of results.

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[Benjamin Leica]

The numbers that appear inside your lenses are most probably associated with the manufacturing and quality control process. These numbers are primarily used by lens manufacturers to identify different lens elements and verify that they are put together correctly.

If you found matching numbers on the front and rear lens groups, it is possible that they belong to a matched set that was thoroughly tested and put together systematically to ensure that they perform at their best.

The numbers may also be used for the refinement of lens element pairing, as you have mentioned earlier. In this process, the manufacturer combines lens elements based on their optical characteristics to create lenses that deliver optimal performance.

[Michael Geschlecht]

Hello M Kelly & Benjamin,

Welcome to the Forum both.

Leitz rangefinder lenses have a similar system for identifying actual focal lengths & serial numbers on different parts of the same lens.

Does the lens in the photograph have a serial number that ends in "292" ?

We don't need to know the rest of the serial number.

Best Regards,

Michael

Edited April 10, 2023 by Michael Geschlecht

[davidmknoble]

While this seems redundant, remember that the last steps typically involve engraving the name and serial number on the lens and painting it in, so some method to put together paired mounts and focusing systems is good to not only making sure tolerances are good, but finding problems in machines etc if they are not good.