This is the king of all joysticks, a real monster. Sega released this in the Saturn's heydey for an astonishing 40,000 Yen. It has eight buttons per player and two start buttons. It's the identical panel and parts found in Sega's Astro City cabinets - though most Astro City panels have fewer buttons.
It's very similar to home sticks internally - a giant PCB connects all the buttons, and there's a dual Saturn encoder PCB tucked away in the center. Unlike most home sticks however the buttons are proper arcade sized, so you can slap in any stock 30mm button from Seimitsu or Sanwa and it'll work great.
The mechanism is a Seimitsu LS-32. There's a small riser inside, welded to the CP and two screws hold the mech to the riser. You can see the mechanism
Some of these sticks have an adjustable guide plate on each mech for 2-, 4- and 8-way operation, while others have only an 8- or 4-way plate. The former is great, and can be adjusted with only two scres, but the latter requires no fewer than 8 screws to adjust. Regardless, the adjustable gate is a great feature marred by the amount of work involved in opening the stick. There's about ten screws on the base, and the panel has to be removed to access the mechs.
The stick bears Sega part number HSS-0130.
Here are some pictures taken of the inside of this stick during a mod.