Collectors also call this rifle the Second Model Allin Trapdoor rifle. 25,000 of these rifles were altered from U.S. Model 1863 rifles at Springfield Armory in 1866. The 40" (to the breech plug, 36 5/8" to the breech block) round 50 Government centerfire (50-70) caliber barrel has an excellent bore with bright, strong rifling.It has the original Civil War era eagle at the breecn and small S and A along the left breech area. The barrel retains its original bright finisah with a few areas of light staining. The 1866 dated breechblock has all its dark color case hardeing. The 1864 dated lock and hammer retain much ot their original dark case colors. The stock is excellent with no cracks or chips, no real wear, sharp edges, and a strong cartouche. The action functions correctly. You will never need to upgrade  this fine rifle!