Wow! And I'm sure that would never be allowed in the USA. But I'm going to call my Neutrik guy and ask for a sample (just for giggles).
I acquired a couple of old amps made by Recording Studio Design (a forerunner of Studiomaster) which have these connectors on the rear.
I have been meaning to get a connector to see if they work but haven't got round to it yet.
Ivan wants one of them for his office display, but they are a bit heavy to post across the Atlantic. If I have a non working one, I was going to strip it of its heavy components to make it suitable for posting.
https://goo.gl/images/aUNYEeSteve.