It isn't a variety, it is a type number.
Yeoman did the two most commonly used books on world coins (Coins of the World, and Modern coins of the World) before 1972 when Krause Publications started the Standard Catalog of World Coins. The Yeoman books gave each different coin TYPE a Y# (Note that was coin types not varieties.) When the SCWC began, it used Yeoman's Y#'s, but each year a few more countries would be renumbered with KM#'s. China is one of the few countries that are still listed the SCWC with Y#'s. Some of China has been switched over. The old Y# 583 is now KM# 892. That is from the 37th edition of the SCWC. From time to time a country will get renumbered but that is probably accurate.