Allow me to retract my earlier comments. This lens does not seem to bear any similarity to what CZJ was making in 1930, the date consistent with its serial number. CZJ truncated its serial numbers when they got to ten million, and the pattern thereafter is rather difficult to comprehend, so this may well be a post-1980 lens. I can find no evidence in II Thiele in either of the relevant sections that CZJ produced a Biotessar after 1930, but this lens is clearly so marked. When the Zeiss Lens List of the late Charlie Barringer becomes available again, it might have some helpful suggestions: Thiele works from the factory recors, and Charlie was an "industrial archaeologist" and worked from field data.
In the meantime, I will ask about this on the Zeiss Ikon Collectors' Group and on the Praktica Users' Group discussion lists. We do have some mighty smart folks over there!
Marc
