I purchased a Beretta BL-3 20 gauge in the mid 1970s. I put thousands of rounds through that shotgun. I handed it down to my son a few years ago and it still going strong. They are great shotguns and a real value on the used market.
As to chokes measuring the amount of constriction if you have a deep bore mic is the best way. Beretta stamped the barrels with either letters or stars. You may have to remove the fore end to see how it was marked. They are stamped, if i remember correctly, on the left side of the barrels the markings are stars * for full ** Imp. Mod. *** Mod and down the line.
Some years were like mine with the chokes stamped on the top barrel
Again congratulations on picking up one sweet shotgun.
