Summary

This is a caliper which is derived from several others here and elsewhere, but not enough from any single one that I felt like it qualified as a derivitive of any one in particular. It is made on a laser cutter and gives readings accurate to 0.05 mm or 1/128 inch. The actual accuracy will depend on the fit of the parts you make.

Instructions

Cut the parts as shown. I included one file with everything (full) or if you need the cutting and marking actions separate, there are separate files for those. There are three layers to the finished caliper. The part "3" is on the bottom and holds the sliding part together. Part "2A" is a bit wider than part "1A", so it keeps everything from falling apart (see detail photo). Parts "2B" and "2C" and a bit narrower than "1B" and "1C" to accommodate the width of "2A". Note that part "3" actually sits upside down - flip it over from the orientation as it is cut. This was done to fit the parts into a smaller area and waste less material when cutting.
The example in the photos was made with laser engraving material which has a white body and an overcoat of black plastic. The laser engraving cuts away the black and leaves the white showing. Depending on the material you use, you might want to use double-sided tape between parts "1A" and "2A". Just be sure not to let the tape get close enough to the edge that it interferes with the operation of the sliding piece.
The holes are sized for US size 6-32 screws to hold everything together.

Vernier Caliper with Metric and US Scales