Friedberg (FR) Number
The Friedberg numbering system was developed by Robert Friedberg, and it is the numbering system used in Paper Money of the United States by Arthur L. and Ira S. Friedberg. It is considered the standard, universally accepted method of describing and cataloging United States paper money.
These catalog numbers are used as a shorthand method of systematically identifying a particular note based on its design, series and signature combination. Each Friedberg number represents a unique combination of these factors.
Krause-Lemke (KL) Number
The Krause-Lemke numbering system was developed by Chester L. Krause and Robert F. Lemke. Chester Krause formed Krause Publications in 1952. Twenty years later, an 800-page Standard Catalog of World Coins made it's debut and the rest...is history. In the nearly 35 years since that massive catalog rolled off the press, list of Krause Publications has grown from just one title to more than 750 titles in print.
Pick (P) Number
The numbering system used in Standard Catalog of World Paper Money series of books editted by George S. Cuhaj is called the Pick Number, based on a numbering system developed by Albert Pick. The Pick Number is considered the standard, universally accepted method of describing and cataloging World paper money.
Albert Pick was a well-known German notaphilist (born 15 May 1922 in Cologne) who published a number of catalogs of European paper money, and, in 1974, the first Standard Catalog of World Paper Money. His collection of over 180,000 banknotes was eventually housed at the Bavarian Mortgages and Exchange Bank (Bayerischen Hypotheken- und Wechselbank, now HypoVereinsbank). This catalog underwent several incarnations, and currently is published as a three volume group. Volume I, called Specialized Issues, includes notes issued by local authorities, which circulated in a limited area. Volume II called General Issues covers notes issued on a national scope, dated 1368 through 1960. Volume III covers Modern Issues dated 1960 to present. Each of the volumes is updated regularly, with Volume III now updated every year, Volumes I and II every 3 or so years. While Pick no longer edits the catalogs (since 1994 the honor has passed to George S. Cuhaj), the catalogs are still commonly referred to as 'Pick Catalogs' and dealers and collectors alike refer to banknotes by their 'Pick number.' Current issues of the three volumes include: