It's a standard 180 degree 5 pin DIN.
Horrible, just horrible things. On every tape deck, open reel, cassette and most tape loops on integrated and preamplifiers through the 1970s. Low level, high noise, poor channel separation and horrible. Just horrible. Try soldering 4 tiny wires and a shield in a nasty housing held together with nothing except melting pins in plastic and you'd be as bitter as I am toward DINs. RCA plugs may be old and simple, but they are a joy to work with!
Then you have the variations, the ones used by Quad on their 34/405-2 etc. And the nasty turntable tonearm "DINs" that were basically whatever they decided- Grace, Empire, Pioneer whoever. Collars, no-collars, long pins, short pins, changes in geometry, screw-in etc.
DIN standard plugs of all types are utterly putrid. There's not a single one I like. For contrast, take the BNC or the Belling-Lee, glorious connectors. The 1/4" phone connector. The Cannon XLR. The PL-259 or the Banana (4mm). All great and none of them DIN related. I would chuck out anything DIN to be honest.
I bet you the Speakon is US designed is it?
You are right, it's a PITA to solder these. You can't see it, but you may see the screw of the Din connector that I used for the motor connection to the IR box of my DIY passive preamp