AZHUR ARMAS, S.A. is who made the SxS.

They were formerly named ASCENCIO ZABALA.
So it could have been mfg'd when they were under the latter name yet as it is marked with the AZ stamping.

I don;t know when the name change came about.

'Ascensio Zabala' was NOT the same company as 'Zabala Hermanos (Bros)'

Added,,
If you want to bring back a little shine to the plates w/o blurring the engraving, go over them with a plain eraser. The 'pink' erasers, we used to call them a desk eraser as opposed to the eraser on the back end of a common pencil.
The eraser on a pencil is generally much coarser and can scratch. A block eraser which if you go to a stationery store to buy one,,will usually come in 3 or 4 different grades of coarseness. Medium or Fine is good to work with.
It's just abrasive enough to clear any oxidation but won't cut any metal from the surface.
It'll shine up inlays as well but don't over do it on soft metal inlay work.