I know this older thread. Hope I don't bore anyone with this information.
The gun shown in the pictures looks like a Mowrey gun works rifle called the Allen & Thurber replica.
Mowrey gun works was around from the 1960's to late 1970's.
They made several style of rifles : a fullstock "Hawken" to a .36 caliber small game rifle.
The Allen & Thurber rifle came in .45, .50, .54 or .58 caliber. With brass or steel furniture.
These rifle could come complete or as a kit.
The 1976 SHOOTER'S BIBLE oddly enough does not have anything listed by this company, however the 1974 GUN DIGEST does...
These are excellent rifles and are very well made, I have shot one in .54 and found it to be accurate with round ball.
Andy