This is a prop box. This coin is the original silver coin, but it has a connected tube that goes directly into the box. When he was holding the box, there was a coin in the hand holding the box, so he put the coin in the tube and the coin went into the box. The tube is buttoned with trousers, so he can take the box without the tube. At this time, you will see coins in the box.

That's because he wants to make sure that the coins eventually go into the innermost bag, and the pipe goes into that bag. When the tube is taken away, the rubber band tied to the mouth of the bag will be wound around the mouth of the bag, achieving a very magical effect.

If you still don't understand, you can buy a stall, just 10 yuan. It is difficult for me to explain the whole structure.