Ken Viani, @ Chose an image sells mounts for the H&R M12, the Winchester M 52 & the Martini Mk III.....

I bought on for my M12 & it fits like it was an original mount from the factory, Ken ships very quickly & is a very nice guy. He replies to emails quickly.

I used standard Weaver rings to mount a Modern scope on the Viani Mount. it is rock solid & looks really nice on the gun.....