You probably bought your Paterson from "JP" Petrizzo, who was hired by Lou Imperato to dispose of the Colt Blackpowder stock after he lost his manufacturing license from Colt.
The markings on the barrel are consistant with those on Italian reproduction Patrsons....I forgot which one. In all probability that gun was a pre-production sample to show what the assemled parts that Imperato was importing would look like after they were finished and blued.
The reason that your letter states that there were no records for this gun is that when production for Colt Blackpowder percussion revolvers ended, since there was no Federal serial number requirement they discarded all of their manufacturing records...possably to forstall any royalty arguments with Colt. No records, no proof!