(Allflex) Using 840 series USDA tags gives you compliance with the USDA Country of Origin Label (COOL) laws. These tags signify to buyers that the animals were born in the USA. Unique ID numbers are stored in and printed on each single use, tamperproof Half-Duplex (HDX) tag. Your farm premise ID number is assigned to the tag number series being shipped to you, and the information is held in the NAIS database.Each tag can be visually verified by looking at the printed tag ID number or be automatically verified with use of a reading device. HDX tags are the best choice when tags will be read using a walk-through reader or in a packing plant, because of their greater read distance.