Evans Rifle with Unusual Barrel

[John Allen]

I just picked up a Evans 1816 Percussion Conversion. All the other parts on the rifle look like a standard 1816 but the barrel does not. Anyone have any ideas what the barrel was originally on? It is stamps US and has a ring around the barrel by the breech. I think the barrel is a brown bess.  It also has the following letters on it that I can still read

4RT - TRI or FRI - RON - N28

Any Ideas?

[John Allen]

[JCKelly]

Never saw a ring like that - it does not at all resemble a Brown Bess.
Would guess at something European which became a Naturalized Citizen.