Dear Mr. Gronau,
Thank you for posting your request on History Hub!
We searched the National Archives Catalog and located the Award Cards, 1942 - 1963 for the U.S. Air Force that includes a card for 1st Lt. Arthur W. Gronau (A02224561) USAF (see Image 831) in the file titled Air Force Award Cards [Distinguished Flying Cross]: Greenawalt, David - Grumbles, Wilbur. These records are digitized and available using the Catalog.
The card cites General Order No. 578, Headquarters, Fifth Air Force, 21 August 1953. We searched the Air Force History Index to the microfilm and located GENERAL ORDERS of the Fifth Air Force for 07-01-1953 thru 12-30-1953 on Reel 0000032077. This reel is in the custody of the Air Force Historical Research Agency (AFHRA). To obtain copies of the general order, please follow the instructions on this page.
We hope this is helpful. Best of luck with your family research!