VSN in PUB notation

A VSN in PUB notation begins with the fixed string PUB (for public). It always consists of six characters, with the format PUBpxx.

PUB	fixed name part to distinguish between private volumes (3 characters “PUB”) = type identifier
p	Catalog ID (catid), (1 character; A..Z, 0..9)
xx	sequential number within a pubset/volume set, (2 characters; 00..31) = sequential number

A maximum of 36 pubsets or volume sets, consisting of up to 32 volumes, can be addressed with the single-character catalog ID.

Examples: PUBA00, PUBA25, PUB502