My daughter and son-in-law wanted me to help them on another Escape Room project, and I gladly excepted. What you see below is something my son-in-lay Matt made a long time ago. It has a linear actuator inside that lifts the top off exposing a hidden compartment (right side). But he wanted to add something different to this puzzle so this is where I come in.
 

I made this trim plate for this puzzle about eight years ago and as you can tell it's been used a bunch. But under that trim plate is just a hollow void making it look like there was more to it, but there's not. What the employees did was push a button in the control room when the people playing the game found and inserted all three keys in the the corresponding slots.

Well all that's about to change because Matt wants me to build something that is functional. That means when someone inserts a key it will have resistance (like a real lock has}, needs to turn 180 degrees and the key needs to stay in place once its turned. Once all three keys have been inserted and turned, an electrical circuit makes a connection and this will open the hidden top.
 

What I'm going to do is use steel and aluminum for this project. The aluminum will have a slot for the key to fit into and go all the way through it. Then I'll fasten a piece of steel to the back of the aluminum so the key will bottom out on the steel piece.
 

Next I machined some slots for the keys in the aluminum pieces. I also drilled and chamfered the steel pieces for a 1/4" flat head screw. The screw will be the pivot point so the block can turn. And each block has the screw hole in a different place which is why I numbered them.