Open a rich looking small wooden box and remove a square of glass.

Pass for examination, if you must.

Onlookers see a wooden box with a slot in the top and the bottom. It looks like it is big enough for a coin to fit thru. But wait, if I put this square of glass in the box it blocks up the holes. But now I have a neat magic trick.
I’ll get a coin to penetrate right thru the glass right in front of any spectators eyes.

That’s just what happens.
The spectators can see the coin literally melt right thru the glass with the box held at eye level.
A helper catches the coin as it falls out. Box is opened and the glass is intact. So is your reputation.

All mechanical.
Great for close-up or parlor.