There was a 10¢ per ½ ounce air mail rate to/from Puerto Rico in effect from March 22, 1929 thru January 14, 1945. Currently, the number of solo uses of the the $1 sheet stamp paying 10 times the 10¢ per ½ ounce airmail rate to/from Puerto Rico is: 1.  

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Description: War Department air mail cover, dated February 11, 1944, with a solo $1 Prexie paying 10 times the air mail rate from San Juan, Puerto Rico to Washington, DC.

Owner/Source: Bob Hohertz web site.

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