Factory Applied Rust Proofing? (PICS)

[fivefix]

I recently removed the door panels on my 30 Tudor and cussed the fool that applied rust proofing to the inside of my doors. In looking at pictures posted by fellow Barner "kwisor", I noticed the exact same looking material applied to the door. I attached Kevin's original 30 Tudor image with the driver's side door visible and a close-up image of my door.

Did the factory apply what appears to be rust proofing material to the inside of doors?