Above: An opposed-twin, chain-drive, Earles-fork equipped Douglas Dragonfly that was up for auction at the Bonhams vintage motorcycle auction in 2013 in Las Vegas. It sold for $17,250 including premium.
1957 Douglas Dragonfly
Above photo: the Douglas Dragonfly 350cc engine.
Below is the 350cc 1953 Douglas Mark V, a earlier version of the Douglas horizontally opposed twin with telescopic forks. It was produced until 1955, when the Dragonfly was introduced. This one sold for $8,050 at the same Bonhams auction in Las Vegas.
Below are pages from the 1948 Douglas brochure for the Mark V.
The Dragonfly in Motorcycle Classics.
The Dragonfly in Wikipedia