The DUKW is a car from GM (General Motors). Under the bonnet: GMC Model 270.
The story
The DUKW (GMC type nomenclature, colloquially known as Duck) is a six-wheel-drive amphibious modification of the GMC CCKW "deuce-and-a-half" 2½-ton trucks used by the U.S. military during World War II and the Korean War.
Designed by a partnership under military auspices of Sparkman & Stephens and General Motors Corporation (GMC), the DUKW was used for the transportation of goods and troops over land and water. Excelling at approaching and crossing beaches in amphibious warfare attacks, it was intended only to last long enough to meet the demands of combat. Surviving DUKWs have since found popularity as tourist craft providing travel across aquatic areas.
What is underneath
Power comes from GMC Model 270. It weighs 13,600 lb empty. These are manufacturer figures carried by Wikipedia and Wikidata, not road-test measurements.
Its place in the line
Nearby in the GM (General Motors) catalogue sit the 1955 Chevrolet and the 1957 Chevrolet.