Stopped by Wes' shop yesterday on my G15. Wes told me a customer dropped off a G15 for some work, but he wasn't sure what model it was. I told him I'd take a look.
Bike looked complete but a little modified - primarily a G15 MkII with CS fenders and seat. It had a magneto and monoblocs, full shrouds on the forks, and the chrome fuel tank found on most of the CSRs and MkIIs. It had standard pipes and fixed footpegs, so I expected to see the engine stamped G15M2.
The engine was stamped P11/1299xx - over 800 numbers past the last supposed P11.
According to everything I've read, the last P11 was stamped P11/129145. If it is a P11 motor in that thing, what's it doing in a 65 or 66 Matchless G15 anyway?
Next time I stop by, I'll have to see if I can find a number on the frame and transmission - and take a couple pics. I'll also look at the rear wheel spokes - CS bikes had heavier spokes than CSR or MKII bikes.