Stamp numbering system - Wikipedia
https://en.wikipedia.org/wiki/Stamp_numbering_systemPhilatelists' traditional method of identifying postage stamps uniquely has long been to number each country's stamps consecutively; Norway #1 is the 4-skilling blue stamp issued in 1855, and so forth. However, this seemingly straightforward numbering system runs into immediate difficulties, which have been solved in different ways by different stamp catalogs.
Stamp catalog - Colnect
colnect.com › en › stampsStamp catalog. Buy, sell, trade and exchange collectibles easily with Colnect collectors community. Only Colnect automatically matches collectibles you want with collectables collectors offer for sale or swap. Colnect collectors club revolutionizes your collecting experience!
iHobb: Stamp Catalogs
www.ihobb.com › c › STAMP_CATALOGSThe Scott Stamp Catalog lists stamps from every country with useful information, including the issue date, the process used to print the stamp, the perforation, and a unique Scott catalogue number. Sort By: View: Scott U.S. Specialized Stamp Catalog 2023 Code: C23S Price: $99.95