Nate/Altair
I have the safe in my possession currently. It uses an ordinary combination lock with a key override. If the key and combination are not used together, a series of poison needles are discharged. It is rather pedestrian, and I am certain you can do better. Plus, the lock is eminently pickable.
Would you like to come over and see it? I can have the smith remove the entire safe, or just the door, depending on what you need.