This Springfield Armory manufactured first variation lock plate is stamped "U.S. / Springfield / 1873" and is for the early model 1873 trapdoor rifle and carbine in 45-70 Govt. caliber manufactured prior to early 1878 and is in very good condition exhibiting a mixture of blue finish with a brown patina and some specks of rust.  (file photo)

Note: Trapdoor rifles and carbines with serial numbers below circa 80,000 would have used this style lock plate.