There are 4 levels in a master key system. They include a change key, master key, grand master key and great grand master key. Below is a list of the order of least access to most:
Change Key: Also referred to the sub-master key, it only opens one lock type, that is all identical.
Master Key: in some master key systems this is the highest-ranking key. It can open multiple doors within a company, apartment complex etc.
Grand Master Key: This type of key can gain access to multiple master key systems. An example would be the doors for multiple business or apartment complexes.
Great Grand Master Key: This key can open all grandmaster, and master key systems. Basically, it can open any door, safe etc. that is within the full master key system.
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