It looks like chipmunk has got the solution of your riddle. Nevertheless I'm curious and just would like to know whether the plugs are still produced and whether this is in France, as I thought after some internet surfing. I'd also like to know what they look like internally.

Interestingly, there is similar a system with regard to position of the contacts but probably built with a completely different philosophy: http://www.becma.ch/GB/index_gb.php?main=membres

This system is called "Marechal" and I remember that I had seen it in the Netherlands already.

Wolfgang