I did some more searching with the info you gave,
I think you may have a Military Rolling block, could you give us a few more pictures such as where the patents are stamped?, I think it will say something like "REMINGTONS ILION, NY USA PAT MAY 3D NOV 15TH 1864 APRIL 17, 1866", as for the caliber it should and probaly is a .50/70
Found what i think you have on Gunbroker take a look at the pics and compare, http://www.gunbroker.com/Auction/ViewItem.aspx?Item=157062682
If it is as described then your looking at a ~$1000+ rifle depending on condition