Hi Dennis,
Yes, that is a typical Jamestown rifle, circa 1840 period. There were over 40 gunsmiths working in Jamestown at that time and they turned out up to 2000 rifles a year. Funny thing, most of them were Quakers.
I think the initials in your photograph are an upside down IIV. About 70% of the Jamestown rifles I have seen will have a roman numeral stamped on the barrel (usually right behind the rear site.) The rifle would have been sold with a matching bullet mold with the same roman numeral stamped on the top flat. That is how they knew which mold when with which rifle.
Look for any other initials or name on the top or side of the barrel in front of the tang. That would be the maker.
Thanks for posting it.
Michael