On our 1988 300TE, the body panels are NOT stamped, but they do have a tamper-resistant sticker of the car's VIN#.
I have found them on the fenders, hood, and rear quater panels (cargo bay side), and the rear hatch.
I have not noticed them on the doors, but will check tonight.
FWIW, Ferrari has one of the most strictest factory policies on repairs. Frames & bodies are not bent or pulled back into shape. An entire measurement of the frame is done. If anything is off, entire subframe and body panels are removed and replaced with NEW parts, and then re-measured. If still off, the pieces to be replaced cover an ever increasing area. Also, only copper hammers that have NEVER touched steel can be used.