This is the late, unlamented (for some) High Standard Model 10B police shotgun made by the late, lamented High Standard Firearms Co.
With a 18.1" barrel and 28 inches overall, it's the smallest package you can squeeze a "street legal" shotgun into. It was designed to be fired one-handed, if necessary, while still maintaining control of your police car.
The 10B was a product improved 10A, which had been around (in tiny numbers) from the mid-70s. Both were five-shot autoloaders encased in a plastic shell that allowed the trigger to actuate the firing mechanism of a nearly-stock High Standard shotgun. The 10A had a built-in flashlight and lacked sights and the second charging handle on the left side.
The 10B had a flip-up front sight, to use with the carrying handle folded down. It also had a distinctive horizontal "shelf" sticking out over the top of the action to act as a gentle reminder to never fire this weapon from the left shoulder.
The specially-modified Kel-Lite (great granddaddy to all modern cop flashlights) was attached by the thumb screw so it was on the left side, and did not interfere with the sights. One problem with the 10A was the recoil tended to batter the D-cells, and break light filaments. The flashlight was an integral part of the upper half of the shell, so if something went wrong, there was no fix short of the factory.
The shotgun, and flashlight, are pretty scarce now, although I keep looking for the flashlight, and an aftermarket magazine tube extension that added two more rounds to the package. This is not exactly a red-hot collector's gun, but having the flashlight helps.
The 10A/B picked up a rep for weirdness for the buttplate, which spun completely around. You couldn't bring it up to your shoulder without wondering where it would wind up poking you. Also, despite the warning to use only magnum or "high brass" rounds, there were complaints of it failing to cycle completely.
All I know is I went over to my friend's house, wrote him a check, filled out the 4473, and then went into his back yard to test it. It was out in the country then, so he had a good-sized berm, with about a mile of scrub woods behind that. We blasted off a box of goose loads, and it functioned perfectly. We shot it single-handed, both resting against the shoulder, and just held out with no shoulder contact. It kicked, but not badly. I was even able to rap off five rounds as fast as I could work the trigger. That was a lot of lead going downrange in just a short period of time.
I've never fired it since, and, being small, it was overlooked in the back of the vault. But it came in handy today when I needed a topic.