Also had the thought that you can easily make a "mirroring" caliper. I can't remember or find what these are called, but are based on registering angular displacement of legs joined by a pivot by extending the legs beyond the pivot--sort of a big "X". Looks like a pair of ice tongs on the measuring end and the "handles" become the "repeater" of the measurement by fashioning one arm of the "X" as a protractor-like scale and the other as a pointer. For a W/T gauge, I spitball that you'd need a straight columnar rod with an anvil to enter the bore much as does the internal leg of the contemporary gauge. The other "leg of the caliper would be a large "S" shape. These legs would pivot on each other at their exact centers and angular displacement (gap) at one end would repeat at the other end 1:1 and could be taken off with another measuring device or compared to a series of "standards". Varying the pivot point to some proportion of the whole would give a readout (movement of the repeater end) in a greater or lesser ratio to the the measuring end. I think the implications for accuracy of moving the pivot closer to the measuring end (movement of repeater much larger than that of measuring end) are pretty obvious. I made one of these yrs ago from aluminum sheet to measure boat planking where the use of a very small bent leg caliper ran into trouble from interference from the width of railcaps because the caliper could not simply be slipped off the planking with the leg gap maintained. This "ice tong" caliper had curved legs to clear the rail obstruction when the tips were in contact with the planking and opposite the pivot the legs turned in an S-curve and became on the measuring end a graduated panel and a pointer. The graduations were of course done "seat-of-the-pants" by setting gap to a known standard and scribing a line on the panel in line with the pointer. Again this is just a suggestion of what may have been.
jack
