It appears as though the author of this piece is actually unknown:
It was long reputed to be the work of Joseph Haydn, but later scholarship suggested that it was actually written by Leopold Mozart. Its authorship is still disputed, however, and other composers have been proposed as the symphony’s true author, including Joseph Haydn’s younger brother Michael Haydn, who purportedly contributed movements to the work. (…) There is reason to believe that the true composer will likely never be known, in whole or in part, given its confused origins and the paucity of related manuscript sources. (Quoted from the Wiki entry on the matter)
Much fun regardless, so enjoy.