Welcome to the Forum, Spikey.

According to your explanation, it looks like your rifle is fitted with Steyr quick detachable mounts, which were marketed in the post-WW2 period, I don’t know exactly when but most likely in the 50s. These scope mounts were - I presume, factory-mounted on new rifles but most likely also sold as spare parts and installed by rifle smiths worldwide; I have similar scope mounts mounted on my MS Model 1903, which was proofed in 1926. These scope mounts are extremely easy to use and much reliable with regards to retaining scope accuracy.

Below are some photos of the mounts on my Model 1903 (but I have found no serial number marking, as you found on your own mounts) as well as of an old Stoeger calatog previously provided by fellow forum member Rothammer.

Front base:

Rear base :

Front mount, with pivot :

Read mount, with windage adjustment screw visible at the bottom:

With regards to windage adjustment, you will find a small screw for this purpose on the rear scope mount; more info on how to proceed for adjustments is available on the bottom right corner of the Stoeger catalog’s third page, see “Sight corrections”.

Good hunting with your new rifle, of which we would welcome photos; by the way, in which caliber is she?

Louis