The Model 1865 First Type Allin Trapdoor design was invented by Erskine S. Allin, Master Armorer at Springfield Armory, as a solution to converting the massive surplus of then outdated muzzle loading rifled-muskets manufactured during the Civil War to a more modern breech loading design. Only 5,000 of these First Model Allins (also known as the Model 1865) were manufactured by altering existing rifle-muskets to the Trapdoor system in order to allow loading from the breech end with a .58 rimfire metallic cartridge. After only one year of production, Springfield shifted to manufacturing the simpler .50-70 centerfire Model 1866 rifles, making any surviving First Models rare and desirable. This example features an "1865" dated lock and "US" marked buttplate. Includes a US socket bayonet.

Very good, scattered light brown surface patina overall, darkened traces of oil-quenched casehardened finish on the breechblock and hammer, and strong patterns of muted case colors visible on the lock with sharp markings. Stock is very good with some handling marks and dents. One of the two extractor screws and the firing pin are absent; otherwise, mechanically fine. The bayonet is very good with brown patina and some light pitting.