Airmail, 1918, 16¢ green. Tied by "Air Mail Service, Wash. N.Y., Phila., New York, Jul 15, 1918" First Flight duplex postmark on Scott Stamp & Coin Co. corner card cover to Washington D.C., Very Fine. Scott No. C2; $800  Estimate $250 - 350. $0 (Image)

Airmail, 1918, 16¢ green. Tied by "Air Mail Service, Wash. N.Y., Phila., New York, Jul 15, 1918" First Flight duplex postmark on Scott Stamp & Coin Co. corner card cover to Philadelphia, Pa., "Send a Letter by Airplane…" slogan handstamp on reverse, F.-V.F. Scott No. C2; $800  Estimate $200 - 300. $0 (Image)

Airmail, 1918, 16¢ green. Top margin plate block of 6 with guide arrow, o.g., never hinged, exceptional centering throughout, rich color and very fresh, Extremely Fine and choice, a gorgeous airmail first issue plate block; with 2008 P.F. certificate. Scott No. C2  $1,500. $0 (Image)