It is difficult to describe the precise markings on the lenses since the markings were different depending on the country that they were sent to. The earliest were marked "Carl Zeiss Jena". Many have the first quality symbol and many have DDR for Deutsche Demokratische Republik (the official name for East Germany). Lenses intended for the U.S. may be found marked "Aus Jena" or "Jena S" from about 1969 when Zeiss West Germany won a law suit in the U.S. Courts against Carl Zeiss Jena over who owned the trademark(s) for Carl Zeiss. The lenses intended for West Germany all were marked this way since the court case there preceded the introduction of the Praktisix. The serial numbers were assigned by some system known only to the East Germans. They may have been assigned annually or by lot or by intended destination or by all of these or none of these. Lenses can be found with 7 digits, 5 digits, and 4digits. One interesting fact is that 4 & 5 digit numbers are found on the last year of production.
Unfinished with leatherette covered focusing ring and a glossy enamel identification ring with white filled engraving. The aperture and focusing scales are red and black filled engraving. The aluminum on these lenses is typically corroded. These lenses were produced from 1956 to 1963, approximately.
Black enamel with a hard plastic focusing ring with raised ovals. The aperture-adjusting ring is aluminum with orange filled engraving. The aperture and focusing scales are red and white filled engraving. It is common to find these lenses with broken focusing rings. These lenses were produced from 1961 to 1963, approximately.
Black enamel with alternating aluminum bands on the aperture and focusing rings. The aperture-adjusting ring is aluminum with black filled engraving. The aperture and focusing scales are orange and white filled engraving. These lenses were produced from 1963 to 1967, approximately.
Totally black enamel (may be anodized) with white filled engraving. During the last few years of production these lenses were multi-coated and have the marking "MC" in red on the lenses. There is a very minor variaton on these lenses, on most the front of the focusing ring is bright aluminum but some have the finish totally in black. These lenses were produced from 1967 to 1978, and the MC from 1978 to 1990 ,approximately.