QR Code stamp
According to the article, "Scanning the QR Code takes the user to a mobile site where the unique code can be entered and view confirmation on the receipt of your mail as well as additional data about its route. Users can find out when the mail was sent, how many kilometers it had travelled, when it reached its destination and more."
The QR Code stamp was produced to mark the 20th anniversary of the issuance of postal stamps by Croatian Post.
According to Wikipedia, a QR code (short for Quick Response code) was first designed for the automotive industry track vehicles during the manufacturing process.
To read the entire article, click here.