The two marks you've found are the identification of the Italian proof houses. They are required on every gun manufactured in Italy, so they do not help in identifying the actual manufacturer. They do prove the gun was made in Italy, however.
The letters AD in a square are the code for year of manufacture; AD means 1978.
If present, the manufacturer's mark will be big enough to easily identify without magnification.
Palmetto is indeed a palm tree, inside an oval shaped outline. Uberti is the letter U inside an outline that looks like the muzzle end of a revolver; Uberti sometimes just uses the name A. Uberti also. Pietta uses the letters FAP, sometimes alone, sometimes inside a diamond shape, and they also will occasionally use just the name F.LLI PIETTA. Davide Pedersoli uses the letters dp inside an oval. The letters DGG, either alone or inside a circle, stand for Armi San Pauolo - the letters are for the company's founders names. ASM means Armi San Marco. Finally, Armi Sport uses the letters AC inside a circle.
The most likely place to find the mark is on the bottom of the barrel near the frame and/or the bottom of the frame in front of the trigger guard. It is also occasionally found on the side of the frame.
