Date of Zeiss Tessar

I have a Carl Zeiss Jena Tessar 13,5cm f/4,5 lens in a dial set Compur shutter for 4x5. Lens serial number is 842XXX. Zeiss lists I see online show 700,000 range serial numbers for 1927 and 900,000 range numbers for 1928 - no 800,000 numbers. The Compur shutter is serial number 258XXX. I’ve seen online dates of 1914 and 1933 for this shutter. The 1914 I’d believe, but I think Compurs were rim-set by the 30s.
Anyone have a good guess on the date of the lens?

I think this is because they earmarked certain ranges of serial numbers for different products, like different batches of camera lenses, binoculars, microscopes, telescopes and other things. The start and end of production of each type of products would start and end with different serial numbers each year. Look at the numbers for 1929 and 1930 for some extra confusion:

1926 From 666,790 to 703,198

1927 From 722,196 to 798,251

1928 From 903,100 to 908,150

1929 From 919,794 to 1,016,885

1930 From 922,488 to 1,239,697

From those numbers we can only say that your lens was made in either 1927 or 1928. Maybe someone has better and more exact numbers for the camera lenses.

From Hartmut Thiele's Fabrikationsbuch Photooptik II Carl Zeiss Jena this would be one of a batch of 500, serial numbers 842,501-843,000. Production of this batch started 15 February 1928.

David

Thanks, David.