I remember my parents having a Sharp amp plus Garrard
record deck back in
the 70s that had similar connections for the speakers, but that's a bit OT
:)
Are you sure you're not thinking of the 2 pin DIN speaker connector which
has one flat pin in the centre of the (cylinderical) plug and a round pin
alongside it? Very common...
I believe, BTW, there's also a 2 pin DIN plug of the normal type (overall
cylindtical mertal chell, all round pins). It has a plastic
switch-operating peg too. It was used on a frw portable tape recorders
for ecternal; PSU/removte control.
-tony