This is, I believe, a 1920s era Stromberg Voisinet tenor guitar. It has no markings identifying it as such, but this shape (called "Venetian") was unique to them, so far as I've been able to figure out. If you're familiar with Kay Kraft guitars, Kay is the more well known company that bought out Stromberg Voisinet about 1930).
I got this at a junk store for a few bucks, had it restored for several more bucks and found out may be worth several hundred dollars, were I interested in selling, which I'm not.
The tenor guitar is similar to the octave mandolin, but with only four strings (whereas the octave mando has four courses of two strings, or eight strings all together). It's a very fun instrument to play. Unfortunately, I'm quite the amateur.
Here, I'm playing "Cluck Ol' Hen," a traditional tune. A third of the way in, I add in a guitar layer to round out the sound some.
Visit more junk stores. Enjoy.