The Lesser Key of Solomon, Crowley/Mathers edition, 1904:
THIS is the Form of Pentagram of Solomon, the figure whereof is to be made in Sol or Luna (Gold or Silver), and worn upon thy breast; having the Seal of the Spirit required upon the other side thereof. It is to preserve thee from danger, and also to command the Spirits by.
The grimoire Grimorium Verum describes this magic object.
The book Sir Gawain and the Green Knight describes this magic object.