What a racket! What a surprise!
Hand a spectator this box, explaining that it must be handled carefully, as it is a very valuable piece of equipment. Take a silk handkerchief and vanish it, telling the spectator that the vanished silk is now inside the box. Ask the spectator to carefully open the box. As soon as the spectator opens the box, it completely falls apart, crashing to the floor with an awful racket! BUT WAIT- the vanished silk is indeed found hanging INSIDE THE BOX! Great comedy routine!
And even if you don't know how to make a silk vanish, you can STILL use this box! For example, just let your spectator hold the box, and tell him that there is a special surprise inside. The "surprise" of course is that the box falls apart when he opens it!
PLEASE NOTE: Because this effect involves dropping the box, expect that the box will gradually become scratched and dinged. You can touch it up as you go, or just allow it to become naturally "aged" over time as you use it in your show.