Super 1970s but also to my eye rather transcendent; this feels to me as much like a piece of end of day pottery (or slag glass) vessel as it does something made for market, though I believe it was produced by Ron Allen/Comanche Pottery (Comanche, Texas, also with production in Oxford, Mississippi and  Lumberton, North Carolina.) Since finding this one I've turned up images of a few others--the forms, with what look to me like applied ribs (a clever nod to/incorporation of coil building), are fairly consistent, but the nature of the swirled clay makes each one very much its own thing. I'm totally smitten with this thing, great and with dramatically different color all the way around. 

5” diameter x 4 1/8” t and in good used vintage condition. Wear to the interior and one tiny surface chip to the top of one rib, very minor.