This is an example of a Civil War Spencer carbine converted to rifle musket configuration by the Springfield Armory in 1871. The Springfield Armory converted 1,109 Spencer carbines to rifle musket configuration by replacing the carbine barrel with a 32 1/2 inch round barrel with three-groove rifling, adding a full length walnut forearm, two barrel bands, block front sight for an angular socket bayonet and ramrod with ribbed head. The new barrel was fitted with the folding leaf Model 1868 military rear sight. The rifle musket conversion retained the original Stabler cut-off and the carbine stock with sling bar and ring. The original Spencer Repeating Rifle Co., markings and serial number "21956" are present on the receiver. The serial number was also stamped on the left side of the barrel immediately in front of the receiver during the conversion. The top of the breechblock is stamped with an "&". The receiver, breechblock, lever, and buttplate have a casehardened finish. The barrel and rear sight are blued. The barrel bands are casehardened and the forearm cap and ramrod are bright. The walnut stock and forearm are oil-finished. There are no Ordnance inspection marks in the usual location on the left side of the stock wrist. This conversion was an Ordnance attempt to modify surplus Civil War weapons for issue in response to the reductions in military procurement spending that followed the Civil War.

The rifle musket is in exceptional, un-issued like condition. The barrel retains nearly 90% plus of the armory blue finish. Nearly all of the blue-black finish is present on the rear sight. 95% of the bright casehardened finish is present on the barrel bands, receiver, hammer, lever and buttplate. The case colors are thin on the left side of the receiver and the left side of the receiver has several spots of light surface pitting. The Spencer markings on the top of the receiver are light. The bore is mirror bight. The stock and forearm are both in very fine condition with minimal storage wear. This is an exceptional example of an experimental Springfield Armory rifle musket conversion of a Spencer carbine.