Aviation Meet cover
The Nutwood Park Aviation Meet, sponsored by the Dubuque Business Men's Association, featured pilot Charles F. Walsh flying mail each day over Route No. 643,001. The meet took place July 20-21, 1912. The route traversed points between the aerial substation at the park and a location near the Dubuque Post Office.
Officials applied a three-line rectangular cachet to the mail, on some pieces as a postmark and on others as a canceling device. Other pieces received this cachet and an additional, undated Dubuque circular double-ring postmark or target killer. Other than manuscript dating by the sender, there is no way to determine whether a piece of mail was flown on July 20 or 21.