Toppin is mentioned in Rosenberger's & Kaufmann's book, "The Longrifles of Western Pennsylvania," with the following information provided on page 134:
Toppin, Johnson, born 1808 in Maryland, working at Charmichaels in Greene County, PA in 1860, working in Cumberland Twp., Greene County 1870-1880. No rifles by Toppin are illustrated in the above book.
Shelby Gallien