Yes they are slightly different, but I'm not sure exactly what areas have been painted. The boot and rear bumper look like they match the rear wings, but I don't think they were painted. Perhaps some clever blending was done towards the rear. There's absolutely no sign of accident damage, or even rust repair. The previous owner also didn't know why any painting was done. It's a mystery, but in my 1.5 years of ownership I've found absolutely nothing wrong with it.
On this forum I saw another early silver c70 coupe that had the same thing going on with the paint, in the same place, so there's a chance that the paint aged badly.
https://www.volvoforums.org.uk/showthread.php?t=305481