It's not quite a prison lock. But it is pretty cool. I couldn't find a tonne of information about it, but it is a Fox Police Lock. Made and used almost exclusively in NYC, the lock is designed to go in the center of a wooden door and holds the end of steel rod. The other end of the rod fits into a notch in the floor barricading the door very securely. When you turn the key from the outside, it slides the rod over in the track allowing it to ride out of the lock as you open the door.

This lock came with a Dyna Lok 7 pin tubular cylinder. I couldn't find much info on this cylinder either.

Locked position. The square tailpiece fits into the round cam on the right hand side of the bolt. The bracing rod rests in the notch on the left side of the bolt and in this locked position it cannot move up because it is blocked by the large piece of metal on the top left.

Unlocked position. The cam slides the bolt to the right aligning the bracing rod notch with the ramp in the middle allowing the rod to slide up and out of the lock as the door is moved inward.

Locked:

Unlocked:

Any one have any experience with this lock or the Dyna Lok cylinder? I thought it was pretty neat.