CROMPTON GENERATORS

I have what I believe to be a 240 volt dc crompton generator set up on a trolley and belt driven by one of my engines. I have 9 no 25volt bulbs wired in series and they work a treat set up like this. What I would like to know is the age of this generator. There is no information plate on the generator but cast into it are" Crompton DB 2 1/2." It is big bit of kit weighing around 11/2 - 2cwt and is of the open wound type. Any information would be most helpful so I can feature it in my display boards at this years events. Not that I am after any prizes for my information boards but I do believe they are essential for the public to read at the shows. Looking foreard to your replys Mark Marlow