Wow. This is interesting: tiny stamps that were also playable records?!?
Known as the “first talking stamps” in 1972, these tiny vinyl postage stamps from Bhutan were totally playable and when the needle was put on the record stamp you heard Bhutan’s national anthem and a capsule history of the nation. Talking stamps were thin plastic embossed records with removable back to expose the adhesive.
I've never seen any of these stamps in person, but looking at the pictures, they appear to be flexies (a "flexi" was a piece of thin plastic that was just barely thick/durable enough to be used as a cheap recorded medium) about the size of a half dollar. If you all wanna hear a couple stamps, WFMU has some audio clips.