I saw a thread this afternoon about PCGS expanding bar codes and now I can't find the thread. But, NSA jokes aside, who uses these bar codes?
http://www.cointalk.com/threads/pcgs-expands-barcode-to-maximize-efficiency.237930/ Well, people use them to verify cert, and to sometimes help counterfeit detection, and also to uniquely track and pull in details on NGC / PCGS registry.
A lot of dealers use the bar codes for their inventory software. It's a lot easier and faster to just scan the coins in than it is to enter all the data by hand.
