This is a 1951 plunger framed model. Unfortunately it is a bit of a bitsa having been built from a variety of components by an earlier owner. The engine and gearbox were rebuilt by SRM after a blow up caused, we think, by an aftermarket non return valve. The engine was handed to SRM in buits and they did a wonderful job of re-building the engine since when the bike has done many miles without more than a smear of oil and the odd drip appearing and with complete reliability.