Looks like a Douglas WW1 gen-set engine for a Marconi wireless, based on the 2-3/4hp motorcycle engine. These were also made under license by Bosch up until hostilities broke out (and presumably after without paying royalties!) The Douglas engine will have "Douglas" cast on the face of the crankcase, hidden behind the flywheel. I seem to recall the Bosh units had their name on theirs too. On the timing side I think, but can not remember for certain. There was a picture of one sent in to the Douglas Club magazine a number of years back that was discovered in France.