Andrew, a great find and fun to play with!!! We all knew that it had to happen sooner or later, I have a feeling that more and more Dyson's will be finding their way to the thrift shops.
This would indicate that there may be a whole pile of rubbish clogging the upper reaches of the cyclone unit. Clogging in that area was a common flaw of the DC07 design.
The amount of grit that appears to have passed through the motor is alarming to say the least!
Grit does seem to get through the cyclone system on Dysons - I've noticed it often on my machines. Never nearly as much as that, though, but I clean my filters regularly! This grit is what the new Core Separator stage is designed to eliminate.