It’s what I would class as machine wiring cable. Long out of production. Seems to be just good quality, multi-stranded tinned copper with PVC insulation. Having said that I’ve tried a few similar types which weren’t worth bothering with. This stuff is excellent though (for audio).
Sounds even better doubled up.
Just to put things in context re. the copper content, this stuff will carry 500 watts all day long at 240V and just be luke warm to the touch.
It’s rated at about 1KW before insulation will get hot at mains voltage.