David Williamson generously answered your question, with some addition information:
Bob your hammer gun was made in 1900 and would be a 3 pin lock with the latest "C style hammers. The joint check was discontinued in 1899.
There were three barrel option available, Royal Steel (fluid steel) at $20, Stub Twist $23, and Good Damascus $25. All hammer guns were sold through hardware or sporting good stores unless for the higher grades. Yours is most likely an F grade.