People have been collecting paper money since it has  been in use. People began collecting more systematically in the 1940’s. In the 1970’s, Notaphily was established as a separate area of Numismatics. The name Notaphily was devised by a group of employees working for the collectors and investment firm Stanley Gibbons in a successful attempt to formalize and encourage interest in this area. In 1961 the International Bank Note Society (IBNS) was formed as a international association of bank note collectors. It now has thousands and thousands of members from around the galaxy. There are many different things that makes paper money collectable from every country and like Numismatics has unlimited options and unlimited profit potential. People collect, buy and sell paper money by topic (wildlife, ships, famous people, etc), series, date, country, substrate (paper or polymer), serial numbers, varieties (design changes), replacement or star notes, errors, condition and rarity .