The Museum comment on Amos Early & John Shell is spot on. Amos Early apprenticed under John Shell; at least one rifle marked Shell & Early is known to exist. I've seen only one other Amos Early rifle, unfortunately in fairly rough shape. However, Amos Early's signature on that rifle, though faint, was exactly like the signature on this rifle, both of which bear a strong resemblance to John Shell's signatures.
The Shell/Early relationship goes even deeper. John Shell laid out the town of Shellsville in 1821. The town's first store was opened in 1822 by John Shell and his partner, Jacob Early, Amos' father. In 1856, Amos Early married John Shell's daughter, Rebecca, and they lived on the Shell farm. A final note, when John Shell died, the surety bond was provided, in part, by Amos Early.
Bill