It is a mains power connector as used on Royal Navy ships and submarines.
The thing does lock into place and is sealed by an O-ring to make a waterproof connection. For those who are into such things it would probably be rated IP66.
If I remember correctly, the switch on the socket locks the plug into place when the power is turned on.
The stainless steel tab on the right hand side of the picture is for pulling the plug out of the socket.
Thay could be any two leaded device, resistors, capacitors, diodes, gunn diodes, zenners, tunnel diodes, constant current sources, diacs, thermistors etc.
My guess is they are gas discharge tubes used for voltage suppression.
Here's my effort, from the one JimB posted earlier. Funnily enough, the plug is almost identical to the ones we used on mining battery packs and chargers for explosive atmospheres. Spring loaded terminals in sockets, circumference contacts for the high impedance intrinsically safe sensing that determines when to apply power after connecting.
More specifically I'd put some(a little anyway) money on it being a white LED, lambertian lens, maybe a "Luxeon III" - data sheet over at https://www.luxeon.com/pdfs/DS46.PDF, part number LXHL-LW3C