This Springfield Armory manufactured late variation breech block is for the model 1866 "Second Model Allin" trapdoor rifle and is in very good condition exhibiting a grayish brown patina with rust staining and light wear. The top of the breech block is stamped "1866 / (eagle head)". The late variation breech block is designed for the late variation square cam latch shank and sideplate which are sold separately.  (file photo)