Looks to be a replica of an 1862 Colt Pocket Police 4/2" barrel, but it has a black finish trigger guard, and .36 cal unfluted cylinder.
Navy models were slab side, yours has the newer Army/Police smooth barrel breach.
Italian percussion gun makers made some bizarre non historically correct configurations based on what they had lying around.
Looks a lot like the Pietta 1860 'Police-Sheriff' model but that was in .44 and had a 5 1/2" barrel.
I checked their historical web pages.
2008, only .36 cal Navy they made were 7 1/2 or 5" barrel slab sides.
2008 all the pocket models were in .31 caliber.
Send them an email.
Europeons are pretty good about serial numbers.
info@pietta.it