I am curious to see the answer on this one myself.
I acquired this original VE3 bumper for replacement use on my yellow Z/28 and believe this one had original paint before being restored last year. You can see overspray at the back of both ends, and some overspray up from underneath where the inner brackets are located. Also looked to have had some overspray along the top inner edges but only slight. Other than that, there was very little paint overspray on the backside of this one. Seen in the last picture, the brackets did have overspray on them.
I don't know if these were pre painted on a buck before they were mounted onto the cars but would have thought they were painted off the car?
Hope that helps you out?
