Astra box lock shotguns are solid, dependable, workingman’s shotguns. If there is any doubt as to whether or not a shotgun was made by Astra, here are the markings one may expect to see.
The actual company name is Unceta y Cia, and the maker’s code found on water table and barrel flats is ‘U.C.', thusly:
Additionally the company name and crest is usually found on the barrels:
Hope this helps.