One key will unlock the treasure chest. You can have a limited number of tickets, say 100, so everyone is allocated a key or have raffle tickets with a chance to win a key which may or may not be the key which opens the treasure chest. The spectacle is having those entitled to a key come an pick their key and try and unlock the treasure chest.
Usually there will be something of significant value in the chest.
You need to have a system to select the order of those who come up to select their key and try and unlock the treasure chest. You could use an online chocolate (prize) wheel for this purpose. This could be displayed on the big screen. See “The Old Chocolate Wheel (Prize Wheel) Goes Online” .
If the keys are not identical you should put them in small unmarked envelops and the ticket holder selects an envelope. To obtain cut keys write to Bunnings and major locksmiths on your organisation’s letterhead and ask if they could provide you with a number of false or miscut keys. Don’t forget to tell them their contribution will be acknowledged and publicised if they do not have an objection.
If you don’t want to use a lot of keys then you can use a three number lock. make sure the lock is one where you can set the combination. You set the combination at 0xx where x = 0 to 9. That way the maximum combination is 100. If you say the combination will be 0xx or 1xx the maximum combination is 200.
Use Random.org to randomly generate the combination you will use. If you are selling more tickets then combinations then you can use Random.org to randomly allocate 100 tickets against the combinations. People who have won combination can then be allocated their turn using the Chocolate Wheel or Random.org .