If a record was revised more than once, the number of the revision was given after the date of last revision. The inclusion of revision data was discontinued in 1999. 1898-November 1968 The Library of Congress employed different LC card numbering systems from 1898 to November 1968, from December 1968 to January 1972, and after January 1972. The length of the LC card number was fixed at twelve characters in all these systems, but the constituent data elements varied. Details of each are summarized below.
Prefixes can be from one to three characters in length.
PhoM php Suffixes. Such data are carried as variable length data and do not affect the uniqueness of the LC card number. When formerly input into machine-readable form, suffixes were separated from the last numeral of the card number by a slash. If multiple suffixes occurred, they were separated from one another by a slash. Suffixes were formerly carried in the MARC record as uppercase characters.