This is an old concert size parlor guitar body made by United in New Jersey. It can be tough to date these as not much is known about the company these days but likely 50s-60s, maybe earlier. Some people claim that the United guitar company took over the Oscar Schmidt factory (the company that made the original Stella guitars, pre-Harmony era) after Oscar Schmidt closed down and sold off their brands, but this theory doesn't seem well proven. Regardless, these guitars do share some things in common with the OS made Stella concert sized guitars.
I have owned quite a few OS guitars over the years, I used to be really into them, I don't own any concert size OS guitars at the moment but I do have a tracing I made on paper of the body outline for a late 30s concert size model. The shape of this guitar is very similar to that tracing, it only deviates slightly in the transition from the lower bout to the waist, with the OS tracing having a more rounded or bulbous transition vs this United guitar. The overall length, lower bout width, upper bout width, and waist width are all nearly identical. The depth of the United guitar is however slightly greater than OS concert guitars that I have had, the side taper clearly different, and the back of the United is flat. Anyway, I just thought this information was interesting, I'm not trying to speculate about a connection or come to a real point. Ha.
Moving on... This guitar came to me with the original finish stripped from the back and sides and the top hand painted over with some very bizarre artwork. I stripped the rest of the guitar with chemicals, and steel wool to avoid sanding as much as possible and thinning the wood, then finished the guitar with black India Ink and Shellac. I built up a bunch of coats of India Ink (which is basically a shellac and black carbon mixture), working that into a levelled black surface over the whole guitar body, then afterwards sprayed some number of coats of spray shellac. I rubbed out the final shellac coats with some micromesh to make everything feel smooth, but purposely left texture in the finish from the spraying. This was in hope that it would give it a bit of an aged look and I think it was pretty successful, in person I think this looks more like a vintage finish than something fairly new (probably three years old at this point).
Aside from the finish alteration, the end pin hole has been enlarged for using an end pin jack, there are also a couple small piezo transducers still glued to the underside of the top (they are glued on with fish glue, will remove easily with water, a rag, and a bit of patience). I did shave down the main ladder brace on the top in the area around the bridge as well. This was done cleanly and made the guitar sound much better than stock. These have birch plywood tops and backs (likely solid birch sides) that are much stiffer than solid birch, so the brace shave I felt was justified. I used the guitar with light gauge strings in open D or D standard tuning and the guitar never suffered or changed geometry in the time I had it strung up, which was until about three months ago. This guitar had a really nice quarter-sawn one piece mahogany neck on it that I am now using on another guitar. Most of these guitars I see have poplar necks and many have two piece heels, so this might be an earlier build, not sure.
This body would be a good candidate for a re-top job I think. A solid spruce top would make it quite nice, or you could re-top with more thin plywood and turn it into a resonator, that was my original plan when I picked it up but I was too curious to see how good one of these laminated stella-style bodies might sound with a good setup. It did in fact sound quite decent, but not as good as a solid wood model still.
Specs:
top & back: birch ply - roughly 0.13" thick
sides: I suspect solid birch, but I'm not certain, do your research if concerned about it
bracing: ladder, one brace above soundhole, two below, no bridgeplate, see pics
body length: 17-3/4"
body depth at neck block: 3-3/8"
body depth at end block: 3-11/16"
upper bout width: 9-11/16"
waist width: 7-13/16"
lower bout width: 13-7/16"
Sold as-is, no returns, please don't hesitate to ask any questions you might have before purchasing.