The Browning is a first class light service pistol of its day. It might be either a .32 ACP or a .380 (7.65 Browning, 9mm Browning Short in Eurospeak.)
+1. FWIW the barrel should be marked either 7.65 for .32ACP or 9M/M for .380ACP. The mag is marked 7.65, but the mags are basically interchangeable. The only differences other than the markings are the number of witness holes and the angle of the feed lips, and the feed lip angle can be adjusted with pliers; however, the difference is so subtle that the mags will often function perfectly with no adjustment at all.
BTW the FN trademark makes this a relatively valuable magazine.
Due to long-term military use, there are many knockoff magazines in circulation; these usually function fine, they're just not as desirable from a collectible standpoint.
Minor notes about the gun:
- They had a standard mag disconnect. The trigger will not function with the mag out unless the disconnect has been removed (which is fairly easy to do).
- The thumb safety doubles as a slide stop, but it really doesn't work well as the latter, particularly if the notch in the slide is rounded off. It's fairly common for it to disengage and allow the slide to slam shut if the pistol is shaken, or simply not to work at all. This can be corrected to some degree by cleaning up the notch with a file, but IMHO it's advisable not to rely on this feature (i.e. DON'T hand the pistol to your buddy with the slide locked back), and you should NEVER use the thumb safety as a slide release while reloading!
- There is no last-round slide-lock feature. You'll have to get good at counting rounds when you shoot it.
- It is normal for the firing pin to project from the breech face when the slide is rearwards. The firing pin actually doubles as the ejector. FWIW I mention this because most modern pistol manuals have dire warnings against using the pistol if the firing pin projects in this manner, but this is not a concern with the FN Browning 1922; as the old saying goes, It's Supposed To Do That.