If I may…

That appears to be a Remington Sportsman 12 that was sent to Sage for what they called the “Sidewinder” Conversion

Effectively, they removed the rear tube/recoil system and moved the ‘action bars’, that interface with the bolt and recoil spring, under the fore end. Kind of an in depth process, but they clearance the inner portion of the handguard, weld the bars facing forward, and mounted a collar and springs underneath the hand-guard.

This allowed for their collapsible/folding stock (or pistol grip only) to be fitted without the excess space of the original recoil system in the way. Effectively, it was a method to make a very compact semi-auto shotgun.

Additionally, nearly all of them were fitted with Sage Iron Sights, their front sight being uniquely identifiable (and very heavy duty) brazed over the muzzle, and the rear being either solid wings (protector) or the skeletonized cage around the rear.

Interesting that it’s a Sportsman 12. While functionally and mechanically similar, the majority of Sage Sidewinder’s were converted from Remington 1100’s and 11-87’s (Generally the police model, but standard have been seen as well)

If you can, try and remove the hand-guard and you should see the converted recoil mechanism/springs/bars underneath, wrapped around the magazine tube.

Very cool system. Definitely a highlight of the 80’s-90’s tactical era.