Dear Tom,
I am replying on behalf of the London Douglas Club machine registrar. The London Douglas Club does keep and publish a register of all the Douglas machines we can track down, (hopefully awakening them from their sleep!!)
I think from your posting you may have 1 digit wrong on the frame number. The machine is a model 2 3/4 WD of of 1922.
Our register shows this bike with frame number 54634, the numbers are often not clear. Non of these machines had frame numbers with 6 digits. The engine number we have is 53199 which is again one number different from what you posted. This could of course be an error in our records. I am sure that your bike is the one on our register, its listed as 1922 WD and numbers so similar cannot be a coincidence. We could be sure if you check the gearbox number we have G6/970, these numbers are quite dificult to read on the gearbox casing.
Our registrar is a Mr Len Boydell who would be only too pleased to receive information on a bike that has returned to the fold!
He can be contacted by email on douglasregistrar@talktalk.net we are very happy to get information to non Club members, the more machines on which we have up to date information improves the quality and usefulness off the register. Of course we would happily welcome you into the Club the "London" part of which is purely historical, members now spread the world over. We also have a spares section making parts for the 2 3/4 machines.
Good luck with the machine, I am certain you will get good and useful information through this forum. They make beautiful bikes to ride, they cruise happily, are easy to start and run very smoothly.
Dave