Cal: Per "New York State Firearms Trade" (Swinney & Rowe) Earl Loomis was born May 18, 1798 and died May 26, 1872. Apparently he was a prolific gun maker in East Hamilton, NY ("Loomis's Corners").
There is an example of an E. Loomis marked 1/2 stock rifle illustrated that is almost identical to yours. (same patchbox, running fox on the cheekpiece, acorns on the wrist, identical nose cap, and tang sight).