1937 Paris Exposition Banner Cancel Postal Cover to US

This is an envelope or postal cover with the Paris France 1937 Worlds Fair Exposition stamp (Scott 322) paired with the Exposition banner cancellation. It was canceled three days after the exposition opened on 17 September, 1937 (the same date as on the stamp). I read the cancel as 3:30 PM 20 September, 1937. The cover is in generally good condition and has slight age discoloration. The stamp is very well centered and interestingly commemorates the anniversary of the United States Constitution. Although not actually a FDC, the pairing of the stamp and exposition banner cancel, together with its early use, make this a collectible cover. Will be shipped in an envelope with a backing board.