Leningrad camera has a protuberance in the body just above camera lens flange. That way ONLY Russian lens fit well with one eception the Russar MR-2 that will not fit! Komura lenses for Leica for example do not fit A vey small and rare Hexanon fits the camera. Normally lenses with external focus lever from Leitz, Canon and other Japanese makers do not fit the camera. Once you have the lens in your hands try to fit them into the camera. Avoid lenses with intenal focusing slides like Hektor 13.5cm and Triotar 135mm They will brake the rangefinder! Regards. LP