This is not expert advice so take it for what you paid for it.
But the writing on the side "Black powder only" leads me to believe that you have a modern replica gun. Also the serial number looks to be engraved. I could be wrong but I would think a gun from the 1800 would have a stamped serial number. Just like the Proof marks.
No guessing about it. It's late 20th century. Navy Arms has only been around since the '50's. Most of their Colt repro Italian imports were from the '70's through the '90's. It's likely Uberti or Pedersoli.I pretty much drew the same conclusion; If smokeless powder didn't exist, why state "Black Powder Only." That said, I can't find one like it so I'm thinking (guessing, actually) it's an earlier reproduction. I can't find any Roman numerals or letter codes to indicate its "born on" date. I'll do a little more research the go buy some caps, balls, and powder. And a nipple wrench.