This is a collectors book of First Day of Issue stamps.  The envelope is a specially created replica of the stamp in gold foil.

These envelops were canceled on the first day of issue at the correct post office. 
Olympic Games

I have one book containing 72 separate envelopes.  The stamps cover the following topics:
  Olympic Games  
  Lighthouses
  Statehood of 100th anniversary
  Black Heritage
  Prehistoric Animals
  Famous Authors
  American Classic Films