Volume II, p.144 & 149 of "Ohio Gunsmiths & Allied Tradesmen" by Don Hutslar, the major researcher of early Ohio gunmakers, lists Jacob Kline as working in Hancock County, Ohio, in the mid-1850s through at least the 1880 census. He was born in PA in 1832. More importantly, Hutslar illustrated a Jacob Kline rifle, similar to yours in stock architecture with slight "bend" in lower butt line, low comb line, no trace of side facings ahead of the back-action lock, and half-stocked with a patchbox that's not identical, but very similar in style. The WV Kline rifles were earlier, more sophisticated, and lacked the "bend" in the lower butt line. There are several "J. Kline" gunsmiths known, but the lateness of your rifle and its stock architecture with a bend in the lower butt strongly suggest it was made by the Ohio Jacob Kline above.
Shelby Gallien