I found a William Battles in the 1860 census who was 27 at the time and his occupation was listed as a blacksmith. Possibly the fellow fought in the civil war then came back to work and made these in 1866
Good detective work.
They could have been made up to around the turn of the century, so POSSIBLY made by his son or grandson, but your first idea seems plausible.
Found someone a little closer to probably the owner. A 22 year old William Battles.......who was a machinist.
In the 1880 census he had moved to Saginaw Michigan which is one town over from me. This has to be him.
Even though they are stamped 1866?