Serial numbers on Spencer weapons is very confussing, as some time the Rifles and Carbines are combined and sometime they are not. You can check several different sources and come away with different numbers. They made more carbines than rifles, and when total numbers are given they are usually talking about both Carbines and Rifles. The total number of 50,000 made during the war may be a combination of some or all of both the carbine and the rifle. It was the 105th Pennsylvania Infantry not the 105th Pennslyvania Cavalry that was issued the Spencer Rifle. They were issued the Spencer Rifle late in the war, when the 105th Pennsylvania Infantry moved to Petersburg, Va. on October 5, 1864, they traded in their Springfield Rifles and received the Spencer Rifle on or before October 24, 1864. With all the changes in the Spencer Repeating Rifle Co. like different company name, new owners, changes in Calibers and to the weapon its self, and the different sites of manufacture, it is hard to pin down an exact serial number. It's a hard duck to pluck, but someone may have the exact answer.