Miser's Dream Glass
The glass where a coin dropped in the glass can be secretly and instantly extracted is an old and standard magic prop. This is an opaque stainless steel version of the prop, (unbreakable, and maintenance free !) that will enable you to perform a novel Miser's Dream effect, or vanish a marked borrowed coin for re-production from another suitable prop.
Produce an endless supply of coins from thin air, and drop them into the glass, - the audience can see each coin drop, and hear it fall. Then dump them out, or vanish them all.
Or have a marked borrowed coin dropped into the glass, and reproduce it from some place else. A very reasonably priced utility prop, which can be used under all performing conditions. Or maybe, if you prefer being a practical joker to a magician, this makes a very deceptive dribble glass !!!