Hi Roger,
To follow up Doug's advice,
Regarding the tank transfers, all those required for the Dragonfly are available from the Douglas Club regalia "man" Jerry Rogers, I see you have written to Reg so expect that you will shortly receive our Club magazine which has details of his totaly unpronouncable address in the wilds of Wales. He will gladly supply you, but obviously will need to know if your bike is black and silver or the stone and green variety. You do not mention the toolbox but this also has a transfer (decal?) on both sides, it is of a scotsmans head wearing a tamashanta.
I assume that as a 1955 model your bike has Douglas brakes rather than the later British Motorbrake hubs, the later type has a detachable rear sprocket, unfortunatly the earlier type Douglas is welded and once worn requires to be turned off and a replacement blank machined to fit. Some owners have rewelded the sprocket others have altered the mountings to allow bolt on. I am sure you will get advice from owners either via this Forum or by asking via the Club magazine.
Regarding the number of Dragonflies in the US, we do have the dispatch records but are aware that most of the bikes have been imported since they have become collectable bikes rather than day to day machines! I will research the details for you but please accept that it may take a couple of weeks, I shall be talking with our machine registrar over the weekend and will raise the point with him.
Dave.