These monestary keys are common enough. But I have always wondered what the lock itself looked like. Here is an example of the lock and how the key fits within it.
Key with it lock door, antique victorien monastery. From 100 to 200 years old very rare, good conditions. - eBay (12 Nov 2011)
This key and lock had a 'Buy-it-Now' bid of $150 (Plus $10 Shipping).-----