Deviating back to Mr Gluhareff, I found this photo on the web of a balsa flying model of the Dart dating from 1939. I suspect this may be the "mock-up" that has been referred to in other sources.
Morning Graeme....we had the Tsybin RS before...I think thats a different spec to the RSR.
LM, just remember stewards who work in a bar have their uses!!