I found a pair of iron calipers with brass bushing marked on each leg "S Colt" a the Hazen Flea market today. The vendor said he picked them up outside of New Haven. I read an article that said
"Enter Hartford native Samuel Colt. Colt’s patented revolver was an important invention, but his truly groundbreaking innovation was the perfection of a manufacturing process that enabled production of 10,000 identical copies of that revolver. Colt and his workers developed precise molds for forging the basic metal pieces, and specialized lathes, drill presses, and milling machines to grind those metal blanks into the finished components. They also used jigs and bearing points to secure the blank pieces on the cutting machines, and precise inspection gauges and calipers to ensure that the finished pieces conformed to exact specifications. These specialized machine tools—machines to make other machines—eliminated the variability introduced by hand forging and filing. Thus, by employing the division of labor, specialized machine tools, and precise quality-control standards, Colt and his engineers were among the first manufacturers to achieve interchangeable parts on a mass scale."
I assume these calipers were from his operation. I'll try to get photos posted when my cell phone recharges. Has anyone seen calipers marked this way?