These appear to be Suhl claw mounts.
The forward base needs to be close to the front end of scope.
So either there is a ring around the front tube (the ocular to me is the back end close to the eye), or you use a germanic scope with bottom rails.
Changing the scope may be a major affair.
But the present scope appears to be quite OK for me - except eye relief which may be a bit short.

Fuhrmann