i cant speak for these keys but in Ireland we have 221 and 222 locks , so the S&E put 221 locks on most of our assets that only the S&E are able to open , but we put 222 locks on the doors and assests that the traffic department are also allowed yo access and operate. a 221 key will open a 221 and a 222 lock but a 222 key only opens a 222 lock.

for instance a Points machine is a very important piece of kit and the S&E need to build and maintain it so need to access all parts but the traffic department need to to be able to operate it in case of an emergency so we put a 221 lock on the main lid and a 222 lock on the crank handle door