That orientation suits enclosures where height above the board is tight, or where the cable bundle needs to run flat against the panel. The shell layout is 1 (DE, E) — the standard D-sub footprint that mates with any male DB9 connector having the same shell size and 4-40 threaded inserts. The 125V rating is typical for signal-level D-subs — this is a signal connector, not a power interconnect, though each contact can handle a few amps in practice if the bundle is derated for temperature rise.
Board Locks and Right-Angle Mounting
On a right-angle D-sub, the board locks are what keep the connector square to the board edge when the cable is tugged or the mating connector is screwed down. Without them, the solder joints take the full mechanical load and eventually crack. The 0.590" (14.99 mm) backset spacing means the connector body sits that far from the board edge, which gives room for the solder tails and the 4-40 jackscrew hardware without crowding the PCB edge.