CadStd

CadStd (CAD Standard) is a CAD program by Apperson & Daughters, available in free and premium versions. It will export data in a number of formats, including DXF, SVG, and HP-GL, but has a native format with a .cad extension.

Files appear to begin with the bytes  (hex), which spells "CADSTD" in ASCII.

Sample files
The freely downloadable version of the program comes with some sample files. In a standard Windows installation, they can be found in.

Links

 * Official site, with free and paid downloads