Whatever it is, it isn't James. James had their own particular style of tank and this definitely isn't it. Nor is it Francis Barnett as they had their filler on the right side of the tank and had their own cast alloy cap with scalloped edges.
From the general outline and lack of badge fixing screws I would say it dates from the late 40's, early 50's when tank transfers were the go before plastic tank badges became fashionable. Could belong to any one of a dozen British Lightweights.
Cheers, Bob
