You are bidding on a 1977 United Nations First Day of Issue Cachet commemorating the 20th Anniversary of the Eisenhower Administration "Atoms for Peace Program" which led to the establishment of the International Atomic Energy Agency (IAEA) in 1957, now located in Vienna, Austria.    

Initially issued in Geneva, Switzerland, the front of the envelope has a stamp that reads "United Nations National Postage Stamp Show, 1977 New York, NY" which indicates the time and place when the item was sold.  

The back of the envelope, in the upper right corner, says, in French, " United Nations Geneva Edition, drawing by Boye Willumsen, Denmark.  

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