Those pesky PLU code stickers that you have to peel off your fruit and vegetables do more than just convey prices to the cashier. If you know how to read them, says Marion Owen at PlanTea.com, they can tell you a thing or two.
Conventional produce gets a four-digit number.
Organic produce gets a five-digit number that starts with 9.
Genetically modified items also get a five-digit code, but that code starts with 8.
4139: Conventional Granny Smith apple
94139: Organic Granny Smith
84139: GMO Granny Smith
If you want a full list of PLU codes, hit up the International Federation for Produce Standards, where you can look up the look-up the look-up codes and find out even more info. For instance, some PLUs are restricted to items grown in certain regions. (4138, for instance, denotes a Granny Smith grown in East/Central North America.) But if you want to decode those at the store, you'd have some memorizin' to do. And if you're really into it, here's the IFPS's PLU Codes User Guide (pdf). [via Lekkercraft]