These guns came out just in time for the American Civil War 1861-1865 and about 200,000 rifles and carbines were made. Almost exclusively used by the Federal army because only the North could produce the cartridges, the carbine particularly made itself felt on the battlefield in cavalry vs infantry engagements such as at Gettysburg. There has long been a great deal of romance attached to this arm and consequently they are a favorite of collectors. That said, a number have been converted to centerfire so that reenactors and other interested individuals can fabricate ammunition using available centerfire cases the original rimfire cartridges having been long out of production. This demand in turn resulted in the production of reproduction Spencer rifles and carbines.
Most all that I've handled, including the two examples that were displayed at the 116th Infantry Museum, have shown signs of hard use. Ammunition was produced through to the 1920s and I have no doubt that was when most of the guns were finally reaching the point that they were irreparable.
Below you can see a couple of videos my friend "Perry Owens" of merry old England has done on the Spencer.