National Parks Airways First Flight cover from Butte Montana to Pocatello Idaho (backstamped). Franked with a #C11 5 cent air mail stamp which was issued for the new air mail rate that took effect on the same day as this flight. So this is a "Rate Change" cover (AAMS #RC19) in addition to being a First Flight cover. Purple rubber stamped flight cachet on this #7 size envelope. AAMS catalog #CAM 26S3, Catalog value $13 (1990).

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