It's a pin!
"Ruptured duck" is a slang term for the Honorable Service Lapel Button awarded between September 1939 and December 1946 to the honorably discharged US servicemen and women of WWII. The pin was embossed with the image of an eagle within a circle, but became affectionately known as the "ruptured duck" by wisecracking soldiers ("ruptured" was a slang term for suffering from a hernia, which protrudes from the abdomen in a way similar to how the eagle's left wing protrudes from the emblem). It was also known by some as the "raped duck." Although the ruptured duck is best known as a lapel pin, its earlier incarnation was a cloth patch sewn to the outer garment of the uniform.
The ruptured duck designated to military police that the wearer was not AWOL and, due to clothing shortages on the homefront, permitted him to wear his uniform for thirty days after his discharge. Some veterans continued to wear the duck on the lapels of their civilian clothing years after the end of the second world war and adopted it as a symbol of veteran pride.
The emblem was designed by Anthony de Francisci and the pins were normally craft of gold-plated brass. However, during a metal shortage in 1943, they were constructed instead from blue plastic and later, when it was realized that blue pins were not discernable against blue suits, gold-plated plastic. A vet who got stuck with a plastic duck was allowed by the War Department to trade it in for a brass one when the metal restrictions were lifted.
The usage of "ruptured duck" was eventually widened to refer also to the man wearing it (that ruptured duck is flying home tomorrow!). Later, the term referred to anything moving quickly (he took off like a ruptured duck!). This was probably in reference to the speed with which discharged men wanted to return home.
It's a plane!
Incidentally, many early WWII planes were named Ruptured Duck. The most famous example is the B-25 bomber Ruptured Duck of the USAAF 17 Bomber Group piloted by First Lieutenant Ted W. Lawson during the Doolittle Raid over Tokyo in 1942. The plane crash-landed in the East China Sea a quarter-mile from Chinese shoreline after successfully completing its bombing run over Tokyo. Miraculously, Lieutenant Lawson and his copilot Second Lieutenant Davenport survived the crash, although both of them were thrown through the front windshield and sustained serious injuries. While in the hospital convalescing from the amputation of his left leg, Lt. Dawson wrote the book Sixty Seconds Over Tokyo, which was turned into a film in 1944.
The 34th Bomb Group also had a B-24 known as Ruptured Duck. The plane flew with the 34th from May 23 1944 to June 7 of the same year, partaking in all of the group's first thirteen missions. Although it wasn't recorded to have sustained damage during the thirteenth mission, it was the last time Ruptured Duck flew with the 34th.
A B-17 airplane of the 91st Bomb group was also named Ruptured Duck.
It's an alcoholic drink!
The Ruptured Duck is also a cocktail!
Mix, shake with ice, and strain into a highball glass. Cheers!