BNF lists online a Necrology of "compositeur Auguste Vern" dated 1854. Not sure if it was posthumous or written the year he died, but it certainly suggests he died by 1854. There is a letter at Worldcat by him to apparently his publishers dated 1831, so his deathdate is between those dates. (fl.1831, several works of his published around 1830, died no later than 1854, so...) Ah. obituary. Died age 85. Bridged Classical and Romantic eras, it seems?... - hard to say?