A fairly slow start disassembling the frame, sub-frame and swinging arm. Here is the disassembly kit:
It seems appropriate somehow to use nice old quality tools to do the work. I think the subframe and swinging arm have never been off since the factory - as the bolts look original and undisturbed.
One nice thing is that the swing arm grease nipple has been used - the bronze bushes and spindle look in very good condition. I took a photo of the arm with the bushes and the spacer / shim fitted in the factory so I can remember which side it fits:
I've bagged the old bolts - though most are only being kept to confirm the size and thread of their replacements.
I've also used a drill and wire wheel to uncover the frame number :
The numbers from the 1960 models initially went from 029364 to 030424. Later in the year the numbers changed to have a 'D' prefix and ran from D507 to D7711, and those were built from October 30, 1959 to July 21, 1960.
So presumably this one is a very late 1959 made bike - of the 1960 model year specification. I just need to find the engine number now and I can send off for whatever factory info is available, and then hopefully we'll know exactly what date it was made.