Originally Posted by
Arne Croell
Well, I saw it pretty late, Dan. Anyway, for most of the f/4.5 versions there was a major redesign in 1927-1929, according to the lists in Thieles book. The 13.5cm one was redesigned 1927 and all lenses manufactured after 1928 used that design; however, the redesign of the 15cm from 1928 did not see production until the 1950's and was still made according to the 1911 design before and during the war. All the longer focal length (18, 21, ...50cm) were redesigned in 1928-29 and mostly manufactured according to that design, but the manufacturing lists occasionally show batches with the old designs in between. Its not absolutely straightforward.
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