AutoSketch

AutoSketch is a discontinued 2D vector graphics and CAD program from Autodesk.

It has native .skd and .skf file formats. .skf is evidently a thumbnail format.

Identification
.skd files are reported to begin with ASCII "".

Sample files

 * https://telparia.com/fileFormatSamples/image/autoSketchDrawing/

Links

 * AutoSketch