Philatelic numismatic cachet

A philatelic numismatic cachet cover incorporates an encapsulated coin or medallion. The combination can commemorate a common event or can be used to date the release of either the stamp or coin. They can be first day covers.

Be aware that encapsulation materials on older items have often not been archival so that coins or medallions have become oxidized over time.  File:US Transpo PNC cover.jpg|US first day cover PNC. 

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