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.
- Spanish windlass
- spank
- spanker
- spanking
- spanner
- spanner in the works
- span of control
- spanspek
- spansule
- span-worm
- spar
- sparable
- sparagmos
- sparaxis
- spar buoy
- spar deck
- spare
- spare a thought for
- sparely
- spare me days!
- spareness
- spare no effort
- spare no expense (or no expense spared)
- spare (or save) someone's blushes
- spare part