A Price Look Up Code is a number often used in the North American and other retail industries. The code or 'number' is found on individual pieces of fresh produce (fruits, veggies, nuts, seeds, etc) and serves to make store check out and inventory control more efficient. It's a system that has been in place since 1990 and is now commonplace.
It's very important to note that putting a PLU code on the product isn't required by law. Therefore, its possible that a product without a PLU code could still be genetically modified or conventional unless stated otherwise.
The PLU code will either be four or five digits long depending upon the product variables. It's worth noting that PLU number can also be useful for consumers as well, not just retailers.
If the PLU starts with a '9' it means that the product is certified organic. '8' it means that the product is genetically modified. If it has four digits and starts with a '6' the product is a fresh cut fruit or veggie. If it has four digits and starts with a '4' then it can be assumed it is conventionally grown. If the PLU has four digits and starts with a '3' the product has undergone an iodizing irradiation treatment.