Help date this Italian Beretta 92F?

If it is an FS gun, the hammer pin will have a very large circular head that actually sticks up above the rear grip on the lefthand side of the frame. In the picture below, you can see it as a black arc poking up out of the left side grip below the hammer and just in back of the two pins that go through the rear slide rail.
https://www.beretta.com/en-us/92-fs-inox/

There is a matching machine cut on the underside of the slide on the lefthand side to accommodate the head of the hammer pin. But it doesn't run very far along the underside of the slide. The idea is that if the slide were to separate, the rear part of the slide would go as far as the machine cut allowed, then bind on the oversize head of the hammer pin. That would prevent it from coming off the rear of the gun and potentially injuring the shooter.

In the picture below, you can see the very back of the machine cut on the slide. It's right next to the hammer. A small square cut on the very back end of the left side of the slide that is the opening of the channel. You can also see the hammer pin in this view and it should be fairly obvious that the top arc of the pin is riding in the machine cut.

Because of the way the machine cut is made, it breaks through into the cut in the slide made to accommodate the swing of the swing of the safety lever on the left side. There's a small hole beween the channel for the hammer pin head and the cut in the slide for the safety lever.


If your gun has the hammer pin with the large head and the machine cut in the bottom of the slide, it's a 92FS.

Keep in mind that the original 'S' mod was being performed as a modification to existing guns during the general timeframe that your gun was made. It's possible that they had a slide that was already stamped as an 'F' that received the 'S' mod to make it an 'FS' before it left the factory.