It certainly is not an HMV original fitting. I seem to recall that these plug/socket connections were related to old car radios, either the aerial connection, or power in, perhaps with an in-line fuse.

Car antenna sockets are similar but do not have the bayonet.

Pickup terminals for radios are usually a plug with two round pins (which explains the oval hole in the HMV cabinet) though there are other types, depending on the brand.

Hmmm. Very odd choice for a stereogram over RCA connectors.

My experience of pick-up connectors on mantel radios were that they were usually octal sockets or those fairly common two round pin sockets on a phenolic base, now hard to come by. On consoles they tended to be spring terminals.

1960s and 1970s models probably went the RCA route. Most local and foreign stereo amplifiers were also using RCA sockets for source inputs by then and either RCA or screw terminals for the outputs. I was thinking more along the lines of 1940s and 1950s table radios.

Good to know. The pick-up plug/outlet doesn't work anyway.
I am going to explore using an AM transmitter to play my old time radio records on it.
Thanks for responses.