Help identifying Jupiter 21M lens mount

Hello

I have a Jupiter 21M 4/200 Serial number 84012071 lens I bought recently on impulse.

I dont recognize the mount?

Any feedback most welcome

This is lens with adapter to modern digital camera. The adapter is put on the lens.
For me it looks like Canon EF or Minolta/SONY A bayonet.

Bus shape of the gold contacts tells me this ic Canon EF.

Alfa mate - thanks for the correct answer

I tried previously removing this mount but it was on that tight I gave up assuming (foolishly) that Jupiter must have made this lens with another mount other than the the standard M42. So I went at this mount again and hey presto it un-tightened revealing the M42 thread -all's well in Nirvana again

Welcome

Hello and welcome to the forum Broto.