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by Erskine S. Allin, Master Armorer at Springfield Armory, as a solution to converting the massive surplus of, then outdated, muzzle loading rifled-muskets manufactured during the Civil War to a more modern breech loading design. 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 Second Model Allin conversion rifles, making any surviving First Models scarce and desirable. This example features an "1865" dated lock, boxed script "SWP" (Samuel W. Porter) and oval script "ESA" (Erskine S. Allin) inspection cartouches stamped on the left stock flat, and "US" marked buttplate tang.

Very good with some scattered light surface pitting on the bright surfaces. The lock, hammer, and breech block have a mostly brown patina with strong markings on the lock. The refinished stock is also very good with faint markings and scattered dings and bruises throughout. Mechanically fine.