Dick Johnson suggested there should be a numismatic encyclopedia. There are already several to chose from, though not all are still in print.

1) W. C. Hazlitt -- Coinage of the European Continent (London 1893 & 1897; Chicago 1974), not a catalog but 750 pages of information on denominations, mints, rulers and a brief historical survey of coinage in all the kingdoms of Europe.

2) R. A. G. Carson -- Coins of the World (London about 1964), similar to Hazlitt but more up to date and covers the whole world; however it lacks the chapters on denominations, mints and rulers.

3) Albert R. Frey -- DIctionary of Numismatic Names (ANS 1917; NY 1947 and 1974), the most thorough of the numismatic encyclopedias.

4) C. C. Chamberlain -- Teach Yourself Guide to Numismatics (London 1960), delightful pocketbook size basic guide.

5) C. C. Chamberlain & Fred Reinfeld -- Coin Dictionary and Guide (NY 1960), similar to the previous but with an American perspective.

6) Richard G. Doty -- MacMillan Encyclopedic Dictionary of Numismatics (NY 1982), a good work though limited.

7) Ewald Jung -- World Coin Encyclopedia (NY 1984), rarely ever seen, I think this is the best of the modern numismatic encyclopedias.

8) Adrian Room -- Dictionary of Coin Names (London 1987), a scaled-down but more up to date version of Frey's work. Room's focus is on the origin of the coin denomination -- that is the origin of the word -- rather than the coins themselves.

9) Joe Cribb, Barrie Cook & Ian Carradice -- The Coin Atlas (London 1990; NJ 2004), a related work, arranged geographically rather than alphabetically. Not really an encyclopedia, but an historical survey of world coinage with lots of colorful maps.

10) R. Scott Carlton -- International Encyclopedic Dictionary of Numismatics (Krause Publications 1996), the latest and most disappointing of the numismatic encyclopedias. Each entry has been translated into several other languages, providing a lot of padding to this book.

In addition to these works in English, there are other such works in German and no doubt other languages. There are at least two encyclopedias of Chinese numismatics (in Chinese), one of them in two volumes.