So I picked up this 1937 Plymouth 2 door business coupe and I'm amazed by how rust free it is. I cleaned the trunk out today and it was covered in a asphalt tar like product. It was lifting off in areas so I decided to remove some of it and I was amazed how preserved the metal was. zero rust, no pitting and the primer looks almost new. Was this tar stock? Has anybody ever seen anything like this before?