Levels of Keying

Lock Industry Standards and Training (LIST) Council describes levels of keying as the divisions of a master key system into hierarchies of access, as shown in the following tables.

Note: the standard key coding system has been expanded to include key symbols for systems of more than four levels of keying.

TWO LEVEL SYSTEM

LEVEL OF KEYING KEY NAME ABB. KEY SYMBOL
Level II master key MK AA
Level I change key CK 1AA, 2AA, etc.

THREE LEVEL SYSTEM

LEVEL OF KEYING KEY NAME ABB. KEY SYMBOL
Level III grand master key GMK A
Level II master key MK AA, AB, etc.
Level I change key CK AA1, AA2, etc.

FOUR LEVEL SYSTEM

LEVEL OF KEYING KEY NAME ABB. KEY SYMBOL
Level IV great grand master key GGMK GGMK
Level III grand master key GMK A, B, etc.
Level II master key MK AA, AB, etc.
Level I change key CK AA1, AA2, etc.

FIVE LEVEL SYSTEM

LEVEL OF KEYING KEY NAME ABB. KEY SYMBOL
Level V great great grand master key GGGMK GGGMK
Level IV great grand master key GGMK A, B, etc.
Level III grand master key GMK AA, AB, etc.
Level II master key MK AAA, AAB, etc.
Level I change key CK AAA1, AAA2, etc.

SIX LEVEL SYSTEM

LEVEL OF KEYING KEY NAME ABB. KEY SYMBOL
Level VI great great grand master key GGGMK GGGMK
Level V great grand master key GGMK A, B, etc.
Level IV grand master key GMK AA, AB, etc.
Level III master key MK AAA, AAB, etc.
Level II sub-master key SMK AAAA, AAAB, etc.
Level I change key CK AAAA1, AAAA2, etc.

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