Those that have no distinct transition between cutting edge and tang, a stub monkey tail, and straight (parallel) scales with no curve, are 1700s. The distinct transition of a tang to edge came in the early 1800s. Somewhere around 1810 to 1820 the scales began to have a slight curve. All this from "Collecting Straight Razors" by Robert A. Doyle. No idea about who made 'em.