Old thread, but I like old stuff, and thought I'd add my two cents here.
I've seen and fired a fair number of Reinhard rifles, and feel this particular one was originally made by him. 1861 is a fairly early date for Peter's rifles, and in that year, was most likely made as a picket rifle, for use with a cloth patched bullet no more than 1 1/2 calibers in length, with the muzzle turned round for use with a guide (piston) starter for starting bullets.
Reinhard was a Mason, and many of his rifles bear this mark. I do believe, as Tom mentioned, that the rifle was re-stocked at some point, as the stock does not appear as though it was done by Peter. It's important to note that even though Peter was a already a skilled maker, he went to work with William Billinghurst for a time, in order to learn to make better rifles. As a result, Peter became a better stock maker, skilled engraver and of course barrel maker. His rifles won more matches, and he became famous throughout the eastern US.
The oval plates on the rifle shown appear to be engraved by a skillful hand; the aluminum inlays do not. I think the oval plates were part of the original rifle, and the aluminum inlays added by someone else. Most Reinhard rifles I see are rather plain, but as stated earlier he made them in higher grades as well. As someone stated earlier, aluminum was a bit pricey in the old days, and I have seen several Ohio rifles using this material.
A nice old rifle, thanks for posting it! Every Mother's Day weekend the club at Canal Fulton OH holds a match for original slug and picket rifles. If you wish to tool up your rifle to use as it was originally intended, please let me know and I can refer you to someone who can do this work. Hope this helps.