anyone recognize this mark?

[fernando]

Quite a curiously marked specimen, this one.
The punctions are known as belgium, amazingly (too) clear and quite (too) many at same time ... i don't usually see all this array of punctions in belgium ordinary pieces, both in the ones i have and many others out there. The frase on the barrel "vero montenegrino" is in italian, easily a popular allusion engraved by the belgium maker for italian trade, but hardly directed to either Montenegro or Persia. Also (too) many and varied seals. The one that looks like persian ... is it actually a real ordnance persian seal ? The one with the keys could be Saint Peter's influenced, though the crown is not Papal, but a classic King's crown ... could it be the ( fantasy ) seal of an Italian gun importer/trader?
The two letters before 1913 are certainly initials, and they would help a lot to figure out things, even if by exclusion.
The most amazing thing is that, browsing the net for vero montenegrino, we can see that some years ago an example with precisely the same marks and punctions as yours, was queried on about the same points. The owner said that it was captured and brought to the States by a WWII american soldier.
I hope some the above will help you relating things at tracking your piece provenance.
fernando