The 180/6.3 Tele Tessar K in black and nickel
Most of the 35mm rangefinder systems limited the length of the longest telephoto lens that would rangefinder couple to 135mm, citing rangefinder accuracy based on the rangefinder length. Because the Contax had a longer base, they must have felt the 180/6.3 would focus accurately enough, and offered it in a rangefinder coupled mount in 1933. The lens was only offered until 1936, and the finish changed from black and nickel to chrome, like most of the lenses from that period. In 1936 the "K" was dropped from the end of the name. It is estimated that less than 2000 of these lenses were built.
