It looks like an ordinary postage stamp, but if you scan it with your smartphone it plays 'Radar Love' by the Dutch band Golden Earring.
This world first from Dutch postal company PostNL can be used as a normal stamp to send letters and parcels. The company plans to issue more musical stamps in the next few months, with well known songs by Dutch bands Cuby + Blizzards and De Dijk.
To listen to the stamp you need to install the Chameleon Explorer app on your smartphone. Scan the code on the stamp and this is what you hear: