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 for use with the .58 rimfire metallic cartridge. The Model 1865 First Model 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by Erskine S. Allin, Master Armorer at Springfield Armory, as a solution to converting the massive surplus of, then outdated, muzzle loading rifled-muskets manufactured during the Civil War to a more modern breech loading design. After only one year of production, Springfield shifted to manufacturing the simpler .50-70 centerfire Model 1866 Second Model Allin conversion rifles, making any surviving First Models scarce and desirable. This example features an "1865" dated lock, a faint oval script "ESA" (Erskine S. Allin) inspection cartouche stamped on the left stock flat, and "US" marked buttplate tang.

Fine, with scattered light freckling on the bright surfaces, 80% of the original black oil quenched case hardening on the breech block, strong case colors showing through heavy freckling on the casehardened lock and hammer with defined markings, and a few scattered patches of very light surface pitting. Stock is good as re-oiled, with a reattached cracked section ahead of the lock, and some scattered dents and scratches. Mechanically excellent.