That is beautiful! Hadn't seen one of these. Do you know if it is related to the beretta 1201?
I'm not too sure how much Beretta took from the original Benellis, but here's a quick history from the interwebz - sorry for the thread hijack!
The 121: Benelli’s First U.S. Import
The 121 was the first auto-loader Benelli imported to the U.S.
The 121 started it all for Benelli here in America when it was brought to the U.S. in 1969. Billed as the fastest cycling shotgun ever made, the 121 began as a 2¾-inch inertia-driven 12-gauge, and evolved into several variants, including the more well-known tactical 121 M1, which had a short 18¾-inch barrel with a fixed improved cylinder choke. The 121 also spawned the SL201—Benelli’s first 20-gauge—in 1973 and the SL80 (1974), a 3-inch 12-gauge that was also offered in a myriad of models: 121, 123, Special 80, and Extra Lusso (the fixed choke barrels where interchangeable between each variant). The SL80 was such a solid design that Beretta—known for its gas-driven autos—later modeled an inertia-driven shotgun, the Spanish-made Pintail, after it.
I’ve never had the chance to fire a 121 series auto (they are very rare in the States), but have seen videos of the guns being shot, and the action, which had no rotating bolt head like modern inertia shotguns do, ejects shells incredibly quick. There are legendary stories of the platform being able to cycle through five shells before the first empty hull hit the ground. The recoil was stout on the 121s as there was no recoil reduction system or buttstock pad. Since the gun weighed under 8 pounds (some were as light as 6½ pounds), it could be difficult to stay on target by the time you emptied the magazine, particularly if you were shooting the M1 tactical that held eight shotshells. The gun’s ability to shoot quickly would have given recoil less time to disperse and the shooter less time to recover. One quirk with this gun: there was initially no magazine release lever on the auto-loader, which meant you had to load the first round into the chamber manually. You could load the magazine tube with shells but could not drop a shell into the carrier from the magazine, and rack the bolt to load it like you can with modern semi-auto shotguns. It was done as a safety measure so the magazine could be loaded, but if someone unfamiliar with the gun picked it up, they would not know how to operate it unless they knew a shell needed to be withdrawn from the magazine tube and inserted into the chamber.
The 121 M1 is recognized by more American shooters than the field variant.
Eventually, a “Benelli Button” was engineered so a shell would drop into the carrier when pressed, meaning shooters no longer had to manually load the gun. The two-piece receiver of the 121 is still being used today in the SBE platform. Removing the trigger group was slightly more complex though. To drop it out, you had to slide the group past a solid piece of metal on the underside of the receiver. Retay has a similar design with its Turkish inertia guns, and it can be a little tricky to re-insert the trigger assembly.
There were four important Benelli shotguns that came before the Super Black Eagle that made the iconic gun successful.
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