The White Heat Treating Company was an industrial metal-treating firm active during the Six inch Indicating Calipers Register Caliper - Direct-reading thickness caliper or graduated outside caliper Register caliper (sometimes called a direct-reading thickness caliper or graduated outside caliper). A vintage mechanical measuring tool used in metalworking, woodworking, or specialized crafts.Design: It features curved legs for measuring external dimensions or thicknesses. Scale: As the lower legs open or close around an object, the top pointer moves across an integrated arc scale to give a direct reading of the thickness without needing a separate ruler Cool Piece - see pictures Caliper 6 in tall (approx) when closed. Max width when open 3in

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