Rare 1936 Beretta 418, Can anyone help me with the history of this gun??

[Armalite15]

First of all I'd like to say Hi to everyone and thanks for helping me. I'm new to the forum.

I recently inherited this 1936 Beretta 418 from my grandfather. He served in the Ninth Air Force in Europe during WW2. The slide reads "P. BERETTA - CAL 6.35 - BREVETTATA GARDONE V.T. 1936 -XIV" and the serial on the slide and frame says "610387."
I can make out 2 of the 3 stampings. The slide and frame have a matching "P.S.F." under a crown, which I understand means it passed the test for shooting smokeless cartridges. It also has "1936" stamped in a square box. The third one is harder to make out but appears to be some sort of shield with 2 rifles crossing each other, forming a "X" inside this shield and is underneath a crown.

Can anyone tell me the history on these handguns and what the 3rd stamp means? Is it possible my grandfather purchased or traded an Italian officer for this gun?

[kanister]

Hi, all the three marks belongs to the proof house, the PSF is what you means, the 1936 in the square is the year of the proof test and the crossed rifles tell us that the proof house was in Gardone VT.
These were not regular guns of the Army, but many high ranks had them for private purchase, so it's not possible to tell from who your father acquired it.