This German made gauge in solid brass offers a combination of inches and millimeters. It features notched jaws for inside/outside measurements and a 1/10th millimeter vernier gauge for accuracy.
I use this tool more than I thought I would. I am often using it to measure chain, jump rings, crystals, spacer beads etc. Sometimes, it's hard to "eye" the difference between 3mm and 4mm or to figure out exactly how big 11mm is, so this tool comes in super handy when you need it.