It looks like koa to me but Im not sure.
I dont see the bindings around the body but pictures are dark and small.
Is there actually a style 0K? or is it just a myth?
As others have said, its mahogany. Doesn't look in too bad of a shape for the late 20's date, but those cracks would probably need repairing - I'd guess it will probably go upwards of $400 in the current market for these. The bridge string slots are certainly in better shape than the one I own; its common to see serious wear from years of restringing which can gouge out the slots.
It has the 1-2-1 (5th-7th-10th) fretboard dot pattern of a style 1 and I think you can see the binding in the first pic.
You may be right about the koa, but it's not a style 0.
my 20s 1k has the same pattern as this, and was the same dark color to boot. It looks like Mahogany in photos but it clearly isn't, especially after a little polishing up. This one could go either way.
Yes everyone is right about 0K's but this is a 1K. I bid it up this morning to about $100 below my limit just for fun but someone has a fairly high bid in there already.
Worth $1,500-ish in premium shape, which this one is NOT. The old koa ukes are much more brittle than mahogany, you need a good luthier to repair them properly.