Hello, Bird. I looked at John Walter's book, that has a Type Study by Roger K. Smith. If I am reading this correctly, Type 1 Boston Bailey 1867-1869, No markings on toe end. Type 2 Boston-New Britain (Stanley) 1869 only All features of Type 1 except Eagle Trademark now stamped on toe end (no number). Other traits define the Type 1, (iron stamp, no lateral, right hand thread adjustment wheel), to name a few. Regards, Lou