"There's only one version of the 21 mm Biogon for Contax RF cameras--the f/4.5 coated version that came out in 1954. You're thinking of the 35 mm focal length where the pre-war version won't mount on the post war Contax IIa and IIIa bodies." I am indeed. I thought there were 21mm pre-war versions too. I am quite sure there are 35mm "coated" versions as well as 21mm. The Jupiter 13s are plentiful But I guess that'S just not the same now is it?