Aviation Exhibition postal card
At the Millbrook Park Aviation Exhibition, Portsmouth, Ohio, aviator Charles F. Walsh flew a pouch from Millbrook Park to a point near the post office, a distance of about two miles. The flights occurred June 28 and 29, 1912. The Post Office Department assigned the route as No. 631,001. About 5,000 cards and covers were flown during the two days.
The three-line marking - "AERIAL MAIL SERVICE / JUNE 27-28, 1912 / PORTSMOUTH, OHIO" — which was generally used to cancel the stamps, bears the dates June 27-28. However, all postal documentation, including authorization letters and the official report of the Portsmouth postmaster (written a week after the event), lists the dates as June 28-29. Since authorities used the same marking each day, sometimes with a Portsmouth double-oval cancel without a date, it is generally not possible to tell on which day a piece of mail was flown.
The postal card shown here, addressed to avid collector Karl Koslowski, a recent Russian immigrant and architect residing in Detroit, Michigan, bears the magenta marking, which cancels the 2-cent Grant stamp. There is no other postmark.