There were some Mark series machines exported to the United States. According to the Works dispatch ledger my Mark 3 Sports was shipped directly to its new owner in New York City, in May of 1948. However there were not a lot of machines shipped to the States, forty-some I think between 1946 and 1954 (and at least one 90 Plus that a friend of the family bought after the New York City Motorcycle show.) There was an article by Jerry Rodgers about export numbers in an old issue of the New ConRod. There have been far more (Pre- and Postwar) imported by collectors and enthusiasts since, than by the Douglas factory.
From article by Jerry Rodgers, first appearing in the Jan-Feb 1994 issue of The New ConRod, the following extracts on USA and Australian exports on postwar models are taken.
AU USA
Mark 1 200 39
Mark 3, Mark 3 Sports 126 10
Mark 4, Mark 4 Sports 99 4
Mark 5 38 0
Competition 1 0
80 Plus 4 0
90 Plus 3 2
Dragonfly 15 0
Totals: 486 55
-Doug
