Magnetically encoded cards, labels tags and stickers bearing identification details, all for use in product security, theft prevention, process control, assembly control, retail and wholesale distribution control, stock control and pricing, product recall and medical diagnosis and treatment, blank magnetic data carriers for use in product security, theft prevention, process control, assembly control, retail and wholesale distribution control, stock control and pricing, product recall and medical diagnosis and treatment, and magnetic readers and encoders for reading or encoding information on magnetically encoded cards, labels, tags, stickers and data carriers