Hello Peter1953,
Re the Rochus Dedler(1779-1822) Symphony in D. I have this on CD (Musica Bavarica MB 75116).
Although it was written in 1815, his style is this symphony is very similar to the middle Haydn & middle Mozart symphonies, probably closer to Haydn. Not unique or distinctive, but very pleasant music all the same. It is a 4mvt work. (6'13,"3'19", 4'04", 4'26").Also on the disc are symphonies by K.J.Toeschi (1732-88),P.P.Sales (1729-97) & W.A.Mozart's K19a.
A more Beethovian symphony is the Symphony no3 in E flat op84 (1825), by T.M Eberwein (1775-1831), albeit, early Beethoven. Eberwein's symphonic style is definately early 19th century, and his treatment of the orchestra, to me at least, indicates his love of Beethoven, Haydn & Schubert. It is in 4 mvts .(11'55",7'38",6'00", 6'32"). 32'15"The symphony is on Weimarer Klassik 2 ,AMU CD #081-2.
Marcus.