These are “scribing discs.” You can use these to scribe around an object at a set distance. Pick the disc that matches the offset you want to scribe (¼, ½, ¾, 1, 1.5), then place the pen or pencil in the center hole and trace around the object. If you choose the ¾" disc, you'll scribe a line ¾" away from the reference. See pictures for example.
I have included two profiles:
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