No, the PX guns were not subject to "proof" at a military base ( unless the PX bought them in the country the base is located),,,,we have had some, came from England, France and Belgium over the years and they came home with GI, and would usually have the green card signed by the commanding officer....my wife still has an old model Bearcat came from Europe around here someplace, with the signed card.....NO proof marks of any kind.........
Proof marks were for acceptance for sale in that country,much like any guns coming here would have the country of origin marked on the guns frame, for example "Germany".........
Nice gun in the pictures, last one we saw with those marks was a 357 mag Blackhawk.........