This Springfield Armory manufactured second or fourth variation lock plate is stamped "U.S. / Springfield" and is for the model 1873 trapdoor rifle and carbine in 45-70 Govt. caliber 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 between circa 80,000 and 380,000 or 490,000 or higher would have used this style lock plate.