This might help a bit. 1 star over PSF means it is proofed to 1200KG/CM the 2 star over PSF indicate 1370kg/CM Italian changed their proof to the higher standard in 1962 I believe. What the above means is the gun was proofed at less then SAAMI load level. I almost bought a Italian Hammer gun about a year ago. It was also proofed with the single star over the PSF. I was going to use it for a turkey gun and wanted the ability to shoot standard SAAMI loads out of it and decided (based on how it was proofed) not to purchase the gun.
Here's a link on the discussion a started before on another forum. You might find it helpful. Tom
http://www.doublegunshop.com/forums/...=199239&page=1