Hi Mate,
It does appear to be an early mayfair base, Im unfamiliar with its handle setup. At first glance it looks like a dep store variant. Msaa colouring and seemingly later than 64.
So, 64 appears a little early, but the metal catcher if correct would put it fairly close. Hopefully some of the 60S/70S Experts will chime in with more accurate model details
You next question, is much more straight forward for me to answer....Your Guess on the engine is close.
The complete engine and cowl assy is Definitely off a 61/2 Sheerline 9 or Standard. The Engine code of 2 DAB is a period correct Sheerline Serial.
However the same engine and cowl style was used on some Mayfair in later models, so its current engine may at least be aesthetically correct, with exception of the starter pulley.
