I agree that there is something odd about the look of the rifle. Stock had been sanded for sure, maybe to make it "pretty". Someone tried real hard to get that collar out of that breech block and gave up. The 1st 1866 I ever purchased had a broken firing pin and badly damaged collar. Took me forever to get that thing out. Pins are easy to find on eBay. Had to order the collar from Al Frasca. I would have a knowledgeable gunsmith look it over before attempting to fire it.
Never Give Up, Never Surrender!