This standard specifies the dimensions and primary image plane position of C-mount connection screws for microscope imaging exits, excluding observation monocular and binocular tubes.
JIS B 7255:2007 Referenced Document
ISO 263:1973 ISO inch screw threads; General plan and selection for screws, bolts and nuts; Diameter range 0,06 to 6 in
JIS B 7255:2007 history
2007JIS B 7255:2007 Microscopes -- Interfacing connection type C