That's a blast from the past (Pun intended). I had one of those when I was just out of high school back in 1982. I bought it used in a a local gunshop that is gone today for $220.
At the time I regretted the purchase as I started thinking, "What a waste of ammo!". It really doesn't have a use, but the muzzle blast and flame during twilight was impressive.
They probably are a collectors item today. I traded mine for a Mini-14.