OverRun
I have been looking more closely at the image of the part on the trolley. (post 588) I have inverted it and shifted the colour markers with this result. Centre right of image there is a rounded star shape, right next to the line marked on the disc.
A witness mark from something adjacent ? to me it looks like the shape found in an oil pump, and beyond the mark itself a discoloured area.
The part you show is a spinning disk that would average the effects of heat tinting over 360 deg.
The best you could do with a photo is to compare the colorations with a normal disk for hints that excessive heat was involved. At this time it's a moot point since the investigation has had time to move beyond this question.