I don’t know how long they’ve been available, but Timothy J. Silverman’s lovely photo (uppermost) just alerted me to the existence of these dual-reading dial calipers that simultaneously report inches and meters on the main scale and the dial. I do remember wanting such an instrument a couple of years ago and Googling around trying to find one with no success. The version pictured immediately above (and, I think, in Timothy’s photo) is this Chinese model imported by TFT Tools, but many other models are available.