I'm the Wiz, and nobody beats me!
It was common practice and is even today to shoot paint on fresh sheet metal such as a tank. Most likely it has been phosphoric acid dipped, then painted without a primer. To be honest, I don't recollect ever seeing a primer on painted chain guards or fenders that have passed thru my hands. The new machines I deal with at work have primer on all the castings and plate steel but none of the sheet metal guards have a primer. I have a guard just like this one, same color, and checked it. I see no primer at all at the chips and scratches like this eBay piece.