Wikipedia
The Perger-Verzeichnis (Perger Catalogue) is a thematic-chronological catalogue of instrumental compositions by Michael Haydn, compiled by Lothar Perger in 1907. Like Ludwig von Köchel's catalog of Mozart's compositions (the Köchel-Verzeichnis), Perger's catalog uses a single range of numbers, from 1 to 136, but like Hoboken's catalog of Joseph Haydn's music, groups the pieces first into categories (symphonies, concertos, etc.) and then sorts them chronologically.
Perger's attempt at figuring out the chronology is, however, so full of mistakes (including the attribution to Haydn of music by others) that later musicologists, instead of trying to amend the catalog (as they have with Köchel's) have created new ones from scratch. The most credible is the one by Charles Sherman and T. Donley Thomas, a chronological catalog of 838 pieces in which each piece is assigned an MH number in that range according to their best guesses at chronology.
Even so, Perger's catalog is still widely used by libraries, music publishing houses and some record companies.
For a more complete listing of Michael Haydn's instrumental and vocal music, see list of compositions by Michael Haydn. The following list only includes those pieces with a Perger number, even when they're not by Haydn. See also Klafsky-Verzeichnis.