In reply to the thread:
Its interesting that each "barcode" (actually, qr code) is unique. For stamps bought with a card, it might be possible to link them back to the purchaser if the Post Office's till system can scan the stamps at the time.
My guess is this is partly about forged stamps, which I read somewhere is more of a problem than I would have thought. Perhaps they want to offer some way for people to print stamps at home, with the qr code offering a way to detect fakes. And maybe some kind of simple app-based tracking service?
I just tried scanning a leftover Christmas stamp and it encodes a text string that looks like it contains decimal and hexadecimal digits:
JGB S111510170310812351000085240521027E887AEC6332FA5801