I found these huge 14-inch nippers at a thrift store. Cleaned of accumulated rust, they turned out to be cutting pliers based on an 1870 patent issued to Frank Carew of South Hadley Falls, Massachusetts. The primary claim on his patent application was for the replaceable cutter inserts dovetailed into the jaws. The tool may have been made up until around the early 1890's.
Contrast this with extremely similar cutting pliers marked "Todd's Patent", patented in 1876. Alloy Artifacts has an entry on them. Note the different shape of the jaw inserts, and the fact that they're screwed into place rather than dovetailed:
Below, pics of a pair I picked up: