Hello,
the CONTAREX "Bullseye" is the heaviest 35 mm camera I know. From a technical viewpoint it is one of the most complicated cameras and a wonder of german craftmenship. If there were several ways to solve a technical problem, Zeiss Ikon always took the most complicated one (see the shutter of the CONTAX). Some camera repairmen got grey hairs working on a CONTAREX. The built in selenium cell is dead on most cameras. The exchangable magazines are seldom light tight due to old seals. It is not possible to focus on the whole fresnel viewing screen, only in the middle. The lenses were superb, especially the 25 mm Distagon, and built like a tank.