This is a civilian baseball cap with an applied Marine Corps insignia on the upturned bill. The cap was given the donor and Medal of Honor recipient Maj. Joseph Foss by his father in 1932. Foss wore this cap throughout his service during World War II. Foss is credited as being the first American fighter pilot to equal Eddie Rickenbacker's score with 26 aerial victories. Foss fought the Japanese in the skies over Guadalcanal and the Solomon Islands, while flying a Grumman F4F Wildcat. He achieved his record between October 1942 and January 1943.
This object is not on display at the National Air and Space Museum. It is either on loan or in storage.