A D-mount1 is a type of lens mount commonly found on 8mm movie cameras.
Throat or thread diameter 15.88 mm (0.625 inch) Mount thread pitch 32 TPI Flange focal distance 12.29 mm
D-Mount lenses have found new uses in the Nikon 1 series, Fujifilm X series, Pentax Q series and other modern mirrorless cameras via adapters.