During my employment at E. Leitz, Inc. Rockleigh New Jersey (1971-1975) it was necessary to regularly visit the Photo Stockroom to inspect newly arrived Leica equipment. One “visit” is especially remembered. #11309 Leitz Canada M mount 35mm 1:2 Summicrons had been received and my co-worker Walter Moffatt (now deceased) and I were studying the new arrivals.
The optics, very early third computation samples just above 2641000, exhibited a protruding aperture control and scooped focusing lever without infinity lock. We noticed immediately the expected E-39 filter threads were absent. Did Leitz Canada forget to cut the threads? Was this a mistake? The presence of the 12504 lens hood suggested use of Series 7 filters. Perhaps the lack of E-39 threads was deliberate?
When the new lenses reached customers, the Leica Technical Service received communications asking about the missing E-39 threads. Customers were not happy. They wanted to use their E-39 filters and without threads they could not. Leitz Rockleigh management was immediately alerted and subsequent production restored the threads. LHSA members who have a threadless #11309 Summicron can advise Editor Rosauer or myself. Perhaps we can ascertain how many units were prepared.