This is a keystem for Monroe K- or KA-series mechanical calculators, which were manufactured between 1920 and 1928. The keystem for the zero digit is different than this, but if you have a metal brake then you can bend this to make the zero keystem (see instructions).The files are 1 unit = 0.001 inches. To make a zero keystem out of this, with the thick leg of the part on the right, scribe a bending line about 0.205 inches from the bottom. Using a metal brake, line up the scribed line with the edge of the clamp, then bend a 1/16 inch radius. This will work out far better than 3D printing the zero keystem version of this part, since you can't really make bends in OpenSCAD. And Blender is a bit beyond me :)