On page 125 of Whiskers paperback Missouri book, they are four rifles made by George Bergner. One is a full stock & the remaining half stocks. The trigger guards on the half stocks are nearly identical to the one you have. The barrel keys & pewter end cap are the same as well.
George Bergner , 1830-1905 Gunsmith Washington , Franklin County, In the papers of U S Provost Marshal for Missouri there is a petition signed by 20 names that George Bergner , gunsmith is loyal to the Union. George etterle, gunsmith lived with Bergner. Bergner held many patents related to firearms.
Henry Bergner. gunsmith, Washington, Franklin County.