There are two different vesions of this lens. The first version of this lens was six elements in four groups, and was unprecidented as a high speed wide angle lens when it was introduced in 1936. The second version was reformulated to include seven elements in four groups,
so that it would clear the thicker shutter curtains on the Contax IIa (and later IIIa) cameras.
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The first version was chrome finished, lacked lens coating (and the red T on the beauty ring), had the aperture scale iside the front rim and stopped down to f/22.
The second version was similar to the first, excepting that the lenses were now coated. This design's performance benefited enormously from the coating, and was amoung the first lenses to be placed into regular production with coating. Early lenses have a silver aperture adjustment ring. Som later examples have this ring finished in black.
In 1946 Carl Zeiss Jena re-introduced the Biogon in an aluminum body. The rear element was slightly reduced in diameter, with a ring around it to protect the glass. Production of this third version was about 2500 units.
Zeiss Ikon introduced the fourth version in 1950. Designed by Dr Ludwig Bertle, it was compatible with the postwar Contax bodies. They are marked Zeiss-Opton. Production was approximently 8000 units.
The final version was the same as version four, except they were marked carl Zeiss, and does not carry the T coating mark on the front ring (although it is T coated). It dates to 1953 and production was about 1800 lenses.
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