- C-mount

screw mount 1″ (25.4 mm) in diameter, with 32 threads per inch,  flange focal distance is 17.526 millimeters. Born for 8mm and 16mm film movie cameras, and 1/3″, 1/2″, 2/3″, 1″, and 4/3″ video formats,  image circle from 5 to 22 mm.
on Wikipedia: