More Aircraft Connectors

MVIMG_20181105_055239

I noticed this round connector as part of my AV display on a recent flight.  It seems to be a DIN connector but I’m not sure that the arrangement of leads is common.  It doesn’t seem to be a PS/2 connector.  I have no idea why the aircraft designers thought this connector was a good use of weight on their airplane.  Did anyone ever use this thing?