I've never seen the List. The ANS card catalog entry reveals it was seven pages long and published in the 11th International Congress of Numismatics.
Perhaps I'm missing something. How can 20,000 items be printed on seven pages? Do 20,000 “items” correspond to 20,000 headings? The Library of Congress sells a five volume set of all their headings in every subject — there are 280,000 in total, for all knowledge in the world. So 20,000 seems high for Numismatics. I'm merely guessing though. I'm not even quite sure what a subject heading is, although this Wikipedia page tries to explain it.
The Library of Congress also has a classification system. Coins are in CJ.
153 Finds of coins
161 Symbols, devices, etc.
1509-4625 Medieval and modern
To get more information about this range one apparently has to subscribe to Classification Web for $325.
Not all books on coins are in CJ. The Library's Numismatics and Philately page points out, for example, that a book listing all coins and banknotes of a country will be found under HG.