It appears that Dunlop (believe it or not they aren't the OEM for the compressor!) in their wisdom used brass for the flywheel/weight on the compressor piston arm.
It has been ground out on the center and it looks like the back side of it in the middle too, and those shavings have gone everywhere.
I haven't worked out what caused the failure - whether it was a loose grub screw which then caused the motor to spin, catch it, get off balance etc. Or whether it happened from the other side. The armature has a couple of big lumps of resin on it - which I've never seem on one before - whether it was to try and balance it from the factory, who knows - but if it's actually caused it to run off balance, then it will have work the front bearing (which there is some play in) and the possibly vibrated the grub screw loose, and gouged out the brass.
The armature has also been scraping against the magnets in the body of the motor, hence all the black shavings in the last couple of pictures... either way - it's properly knackered
'06 4.2 Supercharged Black/Cream "Jess" -- Bought April 2021 (NZ)
'01 4.6 Vogue Black/Lightstone "Snog" -- Bought Jan 2012
'99 4.6 HSE Cobar Blue/Lightstone -- Sold March 2009
'95 4.6 HSE Epsom Green/Tan -- Traded June 2008