The numbers (called Friedberg numbers) in the first column of each listing are the standard, universally accepted method of describing and cataloging United States paper money. The values are presented in the order they appear in the Friedberg book.
Variations within each paper money type include such aspects as size, color, placement or shape of the Treasury Department seal, or signatures of government officials.
The numbers are used as a shorthand method of systematically identifying a particular note based on those variations. In the listings for large-size notes, the Friedberg numbers for a particular design are combined when all the values for the notes in the range of Friedberg numbers are the same. The section on large-size notes is primarily a type listing.
Individual signature combinations for a particular type are omitted unless the price for one diff ers substantially from that for the common notes of the design or type.