It's a US Springfield Military rifle generically known as a Trapdoor. Fires the 45/70 round... Yours is an Infantry Rifle with a mfg date of 1878. This type of rifle was used from 1866 through the 1890's...Spanish American War. what is nice is that U have the orginal bayonet . Your condition isn't that great, so I would say in the it falls in the $500 range...Go look up the Serial number on
WWW.armscollectors.com/srs/htm.
The top $$$ ever paid for a Trapdoor Carbine (US Cavalry use)...was proven forensically to be at the Battle of the Little Big Horn ...was $250K.
If you restore a Antique gun you usually loose half the value as a rule of thumb.
Also if you make sure the bore isn't obstructed your rifle will shoot in it's present condition...obviously you have to look the rifle over to make sure something isn't wrong with it...Generally the 45/70 ammo that is loaded today is designed to shoot in the older Balck Powder guns...but again check this out with your ammo supplier....