O'Neill Nebraska first airmail flight, national airmail week. There is a stamp of a green shamrock that states, "Shamrock Stamp Club, O'Neill Nebraska, National Air Mail Week - may 19-21 1938, First Air Mail Flight O'Neill to Omaha May 19, 1938." The envelope is post marked May 19, 10 A.M. 1938. The letter is addressed to Nebraska Aeronautic Commission Lincoln, Nebraska. The stamp is a six cent bald eagle stamp with Airmail stamped on the top.