I too think it may be a rework military action, not a commercial Spanish. Anyways, if there's a left receiver wall thumb cut-out it's not a commercial action. The Spanish commercial actions have the word "Spain" stamped on the left side of the tang, in a grinded area, just above the trigger.
The British ProofHouses used the Imperial LONG tons (2240 Pounds advp) for proofing, and it does not easily converts to Piezo or even CUP PSI, because the testing methods involved are not the same.
A standard load usually was proofed at 18 Tons per Sq. In. while Magnum calibers were proofed at 19.5 Tons per Sq. In.
With good pictures of the Proofmarks, It may be possible to date the rifle was manufactured except for the year included between 1941 and july 18th, 1950, for wich the proof dating was suspended.
The British ProofHouses used the Imperial LONG tons (2240 Pounds advp) for proofing, and it does not easily converts to Piezo or even CUP PSI, because the testing methods involved are not the same.
A standard load usually was proofed at 18 Tons per Sq. In. while Magnum calibers were proofed at 19.5 Tons per Sq. In.
With good pictures of the Proofmarks, It may be possible to date the rifle was manufactured except for the year included between 1941 and july 18th, 1950, for wich the proof dating was suspended.


















































