A great question, and I'd love to know the complete details of the answer. The original marketed version seems to have been of bamboo. Here is some text from a Chop Chop ad in Genii 1957:
Beauty, in the appearance of the hand-polished, imported, bamboo cup. Beauty, in the durable simplicity of its mechanism. Just imagine, a ball is placed beneath an innocent looking cup. It disappears! . . . Reappears! - - - Becomes a lemon! . . . as it obeys your every wish. In the hands of one who really loves
magic, this new cup-and-ball set has unlimited possibilities!
and some text from a Joe Berg ad for the same product, also 1957:
Magicians have been waiting many years for this
trick to come out on the market Now It's Ready!
A single one-inch Black Ball APPEARS, VANISHES
and REAPPEARS under a beautiful Bamboo RUM
CUP (size of cup 3"x4"). Ball can be removed from
cup; shown empty and inverted mouth down ball
is caused to vanish and spectator may pick up the
cup, ball is discovered under it. UNLIMITED POSSIBILITIES FOR ROUTINES. Comes to you complete with illustrated directions, polished Bamboo
$9.50 from Chop Chop, $9.00 from Berg.