1919 - 1921
In 1919 Duplex announced a light car of conventional appearance but with a most unusual engine. It had eight cylinders, arranged in two rows of four parallel in the block. Each pair of cylinders was connected transversely at the top by a common combustion chamber, with a single sparking plug, and each piston was surrounded by its own sleeve valve. The rest of the car was conventional enough, though quite up to date, with unit construction of engine and gearbox and centre gear lever. Two and 4-seater open bodies were listed, followd by all-weather and conventional saloons for 1921. The cars were unrealistically expensive and the company was in receivership by August 1921.
Source: Nick Georgano / The Beaulieu Encyclopaedia of the Automobile