One for Lutz I think

I'm trying to remember the name of a variation on the 13 pin car socket that was basically a 12N socket with another row of spade connections around it so that you could plug a variant 13 pin caravan plug into but still allowed you to plug a 12N plug into that might still be on a trailer. I don't think Blighty ever used them .... I've only ever seen 1 & that was on a Dutch caravan, but I know that Lutz has mentioned them in the passed. Google just shows a 'normal' 13 pin plug/socket.

TIA