I just bought a Model A Murray-bodied 4-door sedan -- with a title. The car came without a frame and I'm trying to find the VIN. I've been told that it's on the outside passenger side of the firewall. The only tag I can see is a little rectangular tag mounted to the passenger side of the gas tank but anything written on it is hidden by a dark gray oxidation. Is this the right location? How do I clean this tag without destroying the information.

I have the title with VIN, but I just wanted to make sure I could see it clearly on the car in case anyone asked.