cachet

n. capsule; stamp, special mark

In philately, a cachet is a design or inscription, other than a cancellation or pre-printed postage, on an envelope, postcard, or postal card to commemorate a postal or philatelic event. There are official and private cachets; they commemorate everything from the first flight on a particular route, to the Super Bowl. Cachets are also frequently made, either by private companies, or a government, for First day of issue stamp events or 'Second-Day' stamp events. They are often present on event covers.
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Cachet /ca·chet/ a disk-shaped wafer or capsule enclosing a dose of medicine. ca·chet n. An edible wafer capsule used for enclosing an [more]Cachet - Community and Resources

Noun
1. an indication of approved or superior status
(synonym) seal, seal of approval
(hypernym) award, accolade, honor, honour, laurels
2. a warrant formerly issued by a French king who could warrant imprisonment or death in a signed letter under his seal
(synonym) lettre de cachet
(hypernym) warrant
(classification) law, jurisprudence
3. a seal on a letter
(hypernym) seal, stamp

n. tablet, cachet; seal, stamp; fee