This is the high-density shell size 5 (DD layout) — the largest standard D-sub shell, packing 50 circuits into a connector body that typically carries 25 in a standard-density layout.
The flange carries a female screwlock on the mating side, threaded for a 4-40 male jack-screw — the standard D-sub locking interface. This gives positive mechanical retention against vibration and cable strain, and the screwlock is accessible from the mating face so the receptacle can be panel-mounted or left floating on the PCB. The steel shell with tin plating provides EMI shielding continuity when mated to a matching plug with grounded shell.
Housing and environmental ratings
The backset spacing of 0.545" (13.84mm) sets the distance from the PCB mounting face to the mating face — a dimension that matters when the receptacle is paired with a right-angle plug in a tight enclosure, as it defines the cable bend radius and clearance to the board edge.