After years of service, the lock was rusted, painted and filled with dirt and old grease. After several weeks of careful cleaning, paint stripping, polishing and a few chemical chelation baths it's been restored, oiled and sealed back to a mostly-new state.
This is a huge lock. I've placed a standard Schlage SC1 blank next to the key and keyway, for a size reference:
Similar to a number of safe locks, the bolt is drilled and tapped, and can have other boltwork mechanisms attached to it:
The lock would normally be mortised into a cell door or passage door. A single screw holds the top-plate in place. This lock is clearly meant to withstand a significant amount of abuse; the front plate and bottom are just shy of 1/2" thick:
With the cover removed, the lever pack and bolt stump are clearly visible:
A warded plug accepts the key and aligns it with the lever pack:
The levers themselves are huge, shown here again with a Schlage SC1 blank for reference:
Each lever is individually sprung, with a bronze spring permanently crimped into it:
The levers pivot on a small aluminum sleeve that acts as a bearing to help them rotate smoothly:
Once the levers are removed, the plug and bolt can then be removed:
The plug is one single cast piece, and includes both the keyway warding and also a tongue which does the work of throwing the bolt:
The stump on the bolt is notched; it will catch the "anti-pick" protrusions on the levers:
As with the top plate, the sides and back of the lock body are also made from heavy steel, to resist fairly extreme physical attacks:
This was one of my more fun restoration projects, given both the design of these locks and the history of where they've been used. While these locks are still in use (Oliver Diederichsen posted some pictures of a current model in a Guantanamo Lock thread on his blog), they are very hard to come by in original condition: Folger Adam restricts sale of new ones to prison and military applications.
My thanks, again, to Urbex for his help in bringing this project together!