first-day cover 
noun
An envelope bearing a stamp or set of stamps postmarked on their day of issue.Stamps, first-day covers and information sheets issued every month are sent by registered post in a colourful printed cover....
- The one-dollar coin is in a neat first-day cover, with commemorative Norwegian stamps, postmarked on the anniversary day, 28 April, at Bygdøy, the location of the Kon-Tiki museum in Oslo.
- If it is true that stamps and first-day covers reflect the ethos of a country, symbolize what people hold close to their hearts, and are of inspirational value, then Jassi provides reason for introspection.
- world power
- world-ranked
- world-ranking
- world-renowned
- world revolution
- worlds apart
- world's end
- worlds end
- World Series
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- world's fair
- world-shaking
- world-shattering
- world sorrow
- world soul
- world-spirit
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- world-stopping
- World Trade Center
- World Trade Organization
- world view
- world-viewer
- world war
- worldward
- worldwards