i previously believed these may be Venetian in origin, however, if the holes are really conical rather than of even diameter that suggests furnace-wound.
could they be from the Hebron/Fustat/Kano beadmakers or even the heyday of Bida? i also often wondered about the twisted-looking grey ones with a clear glass base...
the Indian drawn cane ones are different. will try to illustrate when i get hold of mine this weekend.