This prototype was displayed as one of the cards in the G.I.Joe 30th Salute Trading Card set.
"The 1993 Leviathan Defender, code named Man-O-War, is the embodiment of
rolling firepower. A gravity-fed magazine releases a column of foam balls
into a chamber, where hand-cranked flywheels can then hurl them at extreme
velocity! The cannon elevates to provide a firing range of over 30 feet,
and the vehicle accomodates and entire platoon of figures. Extremely high
cost kept this vehicle out of production."
Image Courtesy of: Corey Stinson