You say this is a Spencer Carbine: is it marked as manufactured by Burnside (i.e. Model 1865) or is it a Model 1860 cut-down from a 30-inch barreled rifle to carbine length? If it is a Model 1865 made by Burnside, it's post-war. If it is a cut-down M1860 rifle, the serial number (#4841) fits into the range of Spencer rifles that went to Wilder's Brigade. Most all of Wilder's rifles were procured by private purchase rather than government issue.