Sounds like maybe a USRA Target, or a Handy (although I think mine had about a 12" barrel). I've had both albeit many, many years ago. The USRA looks basically like a slab side revolver, the Handy more like a sawed off shotgun.
I imagine either would bring a pretty steep price these days being around 70-80 years old. Both were short run models, with far more USRA's than Handy's because the Army used them. I liked the Handy better myself for it's uniqueness, and because very few of them were ever made, like less than 1/10th of the USRA's production (maybe 200-300 total). Didn't bother me to sell them when I did long ago because I got real nice prices for them - bet they sell for MUCH more today.
Parts for either... good luck. More likely you'll have to make or have a new grip made (or any other parts for them most likely). Short run means not many extra parts were even made most likely. Back when I co-owned a gun shop a fair part of our business was restoring antique firearms, and making parts from scratch was the only option even then, around 40 years ago.
Great find either way.
