Kilmaine

Thanks for the swift identification and interest in my project. The only reference to Vickers  Armstrong Onions I could find did relate to scrapers but the presence of a speedo drive and vacuum control persuaded me that this was unlikely!

The project is a 1925 Rolls Royce Phantom 1 fitted with a 13.5 litre Hall Scott aero engine of the same period. The difficulty is how to gear it up by around 1:2 as the Hall Scott only revs to 1800 rpm. 
The intention is to use it as a road touring car not in competition so refinement and lack of gear noise are of importance.
As the drive arrangement is by torque tube the neatest arrangement for a step up box is to replace the forward section of the torque tube ( it is split 1/3-2/3) with a suitable gearbox arrangement. 
Any thoughts appreciated!

Does anyone recognise this reduction gearbox? The plate refers to Vickers Armstrong Onions, the box is very substantially built with 2:1 and 1:1 ratios controlled by an air shifter. Further clues as to its age: the air shifter piping was plastic. It also has a speedo drive. I am planning to use it on a vintage road car project but concerned that it might be too noisy. 
As an alternative I would be interested in any gearbox that could be used to provide a 1:2 step up and could cope with 250 BHP and 600 ft lbs torque, maybe an epicyclic unit? Thanks