Unless that's an adapter screwed onto an M42 threaded mount, it's not M42. Can't get it off? Is it aluminum?
I've never heard of that lens. Back when I was searching out old USSR M42 mount lenses I ran across a lot of lenses that had been built with mounts for military applications or industrial applications. Some were the same lenses made for consumer photography, but the mounts were for something else. A lot of guys spent a lot of time looking for ways to adapt the weird mounts they found.
Good luck!