This English Triumph model 'Twenty One' 3TA was the first Triumph (in 1957) with a unit block (engine and gearbox fixed together). Twenty One stands for the American capacity measure of 21 cubic inches (348cc) but also for Triumph's 21st birthday. This 3TA has a plated rear and was soon nicknamed the 'Bathtub'. Most of these bikes have been stripped of the plating making this version less common and now a much sought after model.