A nice little clamp I picked up recently. It has a very deep throat, making it especially useful. I had to straighten it and make a new swivel pad for it.
Made of malleable iron, like a lot of clamps. I've no idea what S.H.C. stood for. Someone on the Web has suggested the "Standard Hardware Company." There was a company by that name started in Pensacola, Florida in 1948, but I don't know if they ever made clamps.
Interesting that the clamp is marked "122-1/2." Surely a model number wouldn't contain a fraction? It's a 2-1/2" clamp, so maybe that size and type of clamp was given 12 as a model number?
Below, a 2-inch S.H.C. clamp image snagged from the Web, this one a Model 122: