1933 - 1935
A small Hampshire market town was an unusual location for a car factory, and the J.M.B. was an unusual car in that it was a late example of a 3-wheeled cyclecar, similar to a B.S.A. in appearance. It was less powerful as it used a 497cc single-cylinder J.A.P. engine, mounted behind the seat and driving the single rear wheel by chain. It was available in side-valve form in the Gazelle standard model for the price of £75.50, and with ohv in the Mustang sports model for £91.35. The frame was of ash and on the 1933/34 models the bodies were in fabric, but for 1935 steel panelling was used. A prototype 4-wheeler of 1935 with 350cc Villiers 2-stroke engine never went into production.
The initials stood for the makers, G.H. Jones, R.W. Mason and C.S. Barrow.
Source: Nick Georgano - The Beaulieu Encyclopaedia of the Automobile