I am in the process of restoring a Prentiss vise as well; a Bulldog 51. I found some old catalog cuts on line from the late 1800's thru early 1920's. The catalogs refer to the vises as being "japaned". Japaning is a black lacquer as far as I can tell. I don't know the gloss level. I used Rustoleum Black Appliance Epoxy.