hatman,
Your Remington RB is indeed assembled/finished and sold by David Pedersoli Co. (indicated by the oval with the initials DP, for Navy Arms Co.)
It may indeed be "old" stock. Assembled for Navy Arms in this configuration probably two years or more ago.
Pedersoli has long held very high quality in fit and finish of the firearms they build. Pedersoli also has some of the best mass produced barrels on the market today!
I hope you find this info helpful.
My best,
PS,
As a side note;
The US Model 1841 Rifle (aka, Mississippi Rifle) was manufactured by the National Armory at Harpers Ferry (and a few other contractors) from 1844 until 1855).
These were manufactured with .54 cal. bores (later, many of these were altered to .58 cal. between 1855 to 1862), ALL were manufactured with 33 inch long "Round" heavy or bull "rifle" length barrels.
Blair