Mine to magnet. The 26 companies upstream of the makers — who digs the rare earths, who separates and refines them, who casts the magnet-grade alloy, and who builds the magnetizing fixtures that write a coded pattern in the first place.
The magnetizing fixture is the real gatekeeper of coded magnets — whoever owns the fixture owns the part. See how that fits the whole picture in The Whole Magnetics Catalog.