Thanks Tigerchips, I really appreciate the response. Imperial "Wide Panel" is a great candidate, but this particular form is nowhere in evidence on the net! There's a cuspidor currently on eBay going for over $90 described as "rare" and "one of a kind." (Sure....) Anyhow, I suppose it's possible that this, too, is a rare form. It's such a pleasing and simple shape, though, that I seriously doubt they produced just one!
Charles.