Is this a J.A.G., made by J.A.G. Cars of Thames Ditton from 1954-6?
Forerunner to the RGS (R.G.S. Automotive Components Ltd of Winkfield, Windsor), made by John A. Griffiths, originally sold with the Ford 1172 cc side-valve engine then later on with an MG lump. Apparently about 50 were sold.