I am posting this for Dick Gadler. I am sure he will comment further.
This rifle was made by Thomas Oldham of Bedford County. PA, most likely in the early 1840s, before he went to Iowa.
Curiously, the gun has different calibers and both barrels are rifled. One looks to be about .44 and the other at .48
The barrels are 34 inches in length and each has its own sights, but there is some stripe.
The stock appears to be mostly plain maple.
This is a fairly heavy rifle, about 12 pounds.
Jim Whisker conjectured that this rifle was used principally for hunting bear.
Photography courtesy of Dr. Bill Paton. Thanks Doc!