Feel I should know this, but do think it is British, although can't now recall a name - sure I have seen little mushroomy things with this sort of surface. Am I correct in thinking the finish is what is called a stannous oxide iridescence? About 200mm tall and probably a very deep purple glass looking like black - and it is definitely cased with clear underneath the surface. The top rim has bee ground, polished and bevelled - quite a quality piece. Hope someone can remember the name for me, and if I am in the wrong place my apologies to all. thanks for looking.