Raff, I can't help with the age but went to the safe and checked the s/n of my two Tolley's.
My laminated steel 10 2 5/8" underlever non-rebounding 5 dram roundball gun is s/n 3335. Based on the NR hammers, 'light' charge as 10 rifles go, and short case length my best guess puts it 1875-77?

The other is a bar action top lever 318WR s/n 44121 that I guesstimate 1914-1918.

I know Tolley retailed a lot of guns, but does anyone know if any records exist? What caliaber is your rifle?

Bob