This is on a rifle that is for sale locally. Is the numbering on it correct? It looks like a 359 proofed mount but on a G43 duv 44 rifle.
View attachment 220874
It appears to be an original mount, with the rifle number and scope number stamped into the mount. Hopefully, the matching scope is still on there.
This does not appear to be your typical/common style of mount. More pics would show more details for sure.