I'm not sure how you define a "Symphony Orchestra", but isn't there a
piccolo in the score of Handel's "Water Music" that predates Beethoven
5 by about 50 years (?).  [107 years: 1717 vs 1824.  -Dave]

And aren't there trombones in Monteverdi's "Orfeo"? Although, that said,
the opera house orchestra has always been different to the symphony
orchestra (e.g.  had horns way before the SO did).

Sam Kemp