Biohazard
Dan,
That paint on the valence is lightly done and seems it could easily have been washed off over the years! That most likely explains one side and not the other.
I have been helping a guy and his 69 B5 RoadRunner that swore his core support was never blacked out from the factory (Original Owner)! He hit a tree in 71 and had to have the core support replaced but still had the original. He pulled it out of its hiding place and there was the black. At first he said it was dirt, then looked closer and saw it was paint! Very thin paint!! He is now rethinking and will likely get out some paint. This car is # 13 off the Lynch road line and a Hemi super track pac 4spd car. To important to not get correct for him.
I think someone was in a pit on the line and just free hand sprayed them and probably had a mask for the valences.