@Horton , these are Verniers , they pre - dated the dial calipers. Out of habit , people call dial calipers " Verniers " The top numbers are imperial , bottom is metric. You look to see where the zero of the moving jaw ends up , look at how many lines ( each one is .025 ) it is past the number then try to figure out which line is lining up on the scale of the moving jaw. This measurement is .462 , maybe ? Sure glad they invented dial calipers before I started needing them at work.