Asahi Optical introduced their first camera in 1952. It used interchangeable lenses w/ a 37mm screw mount. Asahi based their camera on the Praktica Practiflex.
Asahi Pentax M42
It's called the Pentax screw mount but it was designed by Carl Zeiss and KW in 1938 and went into production in 1949 with Contax S and Praktica cameras. Early m42 lenses did not have an automatic aperture (preset). On 1956 Contax added a semi-automatic aperture on the Contax F. Pentax followed suit in 1959 with the Pentax K. Fully automatic m42 lenses became available in 1960.
M42 semi auto
Pentax made two 110 cartridge film cameras. They only made three lenses for them. These lenses are collectible so remember this mount. Actually, the lenses have Pentax 110 written on the front ring,
Pentax 645 / 67
Pentax medium format cameras are highly regarded and most bodies are manual focus. The 645N mount is still in use today and manufactured by Ricoh. The 645N is the only series with autofocus capability. See Ricoh. The current 645D and 645Z dgital bodies use the 645N AF mount. The older manual focus 645 lenses can be used on the new digital bodies.
Pentax 645 MF
Pentax 6x7 MF
Pentax 645 N AF