I did speak with the owner. He said this was built in 1965 to replicate a 1937 model. Question is....What brand. Opposed pistons look like BMW..Bavarian Motor works. Could also be an NSU...Necarsulem Valley. Someone suggested Zundaap. Had one of those. Hard on the butt and spine. You in the U.K. know these things better than I. Ring a bell?