Yes, it is a black fridgie.
So far, here's what I've been able to learn about it. First, it is the same size and shape of any other 503 (large) refrigerator dish. Second, the clear glass lid is not original. As far as I've been able to gather, there are no other all-black pyrex pieces except some mugs; this is the only size and shape all-black dish ever made.
(Rodney Kent made mostly hammered aluminum ware that sometimes had Pyrex-made inserts. Other than that, I don't know much about them. Someone posted the other day about a turquoise Starline set, which would be approximately the same era.)
I'd love to find the right lid and cradle, but for now I thought it would look great with my pink fridgie I got a while back. I think this is the beginning of a great alternative set in one of my all time fave color combos- now to find the 2 baby ones in pink!
Anyone ever seen one of these before or have more info?