Looking around some more shows that the PSF with two cogged star wheels above it is a re-enforced proof for shotguns with longer than 70mm (2 3/4") chambers. This law took effect 2 November 1962.
The stars are the degree of choke of the barrels with one star being full choke up to four stars being Improved Cylinder or 1/4 choke. CL designates Cylinder choke (no restriction).
The year of proof is also marked with a coded system beginning in 1945 with the Roman numeral I. So your XIX would be 1964. It wouldn't use the Year of Mussolini as then the proof marks would have a crown above them.
As to the monogram to the left of the proofs and below the year mark, I'm not sure but I would hazzard a guess that it is the manufacturer's monogram (similar to the way H&K uses the HK as their monogram on their firearms).
Your photo of the side view also shows some marking on the barrel just in front of the breech. Is that wording or some decorative engraving?
BTW my info is coming mainly from The Standard Directory of Proof Marks by Gerhard Wirnsberger with some support from The Official Guide to Gunmarks: The Ultimate Gun Identification Guide! by David Byron