After looking at the number of keys I had on my keyring for the same building, and making some quick comparisons, I started thinking about the possibility of generating a master key from the quite freely distributed zone keys, for academic reasons alone. This would be an interesting lesson in image processing.

 
The General Idea:

• Scan each key in colour/grayscale
• Automatically convert image into a 1-bit profile of the key
• Automatically Rotate image so that all keys are in the same orientation
• Automatically section the key to isolate the teeth
• Find the central location on each tooth from key sets (all local max/min)
• Define Integer values for all tooth-height possibilities
• Define each key as a set of these integer values
• Compare similarities and differences
• Option to precategorize with key zone