A simple printable caliper without using supports.
You will only need a little glue to weld the two frames.
Each complete turn of the central wheel corresponds to one millimeter of opening / closing of the beaks.
The central wheel has ten lines which (theoretically) would allow to also calculate the decimals of millimeter.
Obviously it is not an absolutely precise instrument and much depends on the precision of the print.
The stl models do not foresee any tolerance (apart from that of the threads) and it is therefore necessary to set it when using the slicer (for example horizontal expansion in Cura).
Using my Ender 3 and a black Geetech pla filament I printed this model with a resolution of 0.2 mm per layer with a nozzle of 0.4. I set the horizontal expansion parameter in Cura to -0.034 mm. Temperatures 205 for the hot end and 60 for the bed.
The result was quite satisfactory and the caliper also has fair precision.
Happy printing !!