The full title of this catalog is: Histoire numismatique de la révolution française, ou description raisonné des médailles, monnaies, et autres monumens numismatiques relatifs aux affaires de la France, depuis l'overture des états- généraux jusqu'a l'établissement du gouvernement consulaire; par M. H..... avec planches.
This catalog deals with the medals and coinage of the French Revolution and the Directory from 1789 through 1799. It's 927 entries cover a wide variety of numismatic material. It is a frequently cited source and adds considerably to the collector's ability to reference his collection. Bramsen omitted this period from his consideration because of the completeness of the catalog. About it he said:
"For the period from the beginning of the French revolution (27 April 1789) up to 18 Brumaire an 8, (9 November 1799) there exists the famous work of M. Hennin: Histoire numismatique de la Révolution française, Paris, 1826. There is no need of further praise for that book; M. Hennin has once and for all achieved his goal in such a way that his successors cannot dream of doing anything more than making a supplement containing the pieces —few as they may be— which escaped his laborious researches."
I would note that the only discrepancies would appear to be related to British medals and tokens and some German jetons. There are a remarkable number of them referenced in the catalog but in some cases other medals, etc. produced at the same time don't show up. Still, as a knowledgable friend reminded me, "The fact that his work has been reprinted shows that it remains the catalog for that period."