Locking 4pin DIN Plugs used by Naim Audio/Chord - Brand New - Genuine 'Preh GmbH' - Single Plug
These DIN plugs are the ones used by Naim and Chord on their own leads and are the type that twist lock onto later (Olive onwards) Naim sockets.
Link to technical specification below:-
http://www.prehkeytec.com/fileadmin/user_upload/german/Produkte/Steckverbinder/Stecker/71430series.pdf
Thanks for Looking...