Joseph Schuster (1748-1812) was born in Dresden, capital of the Kingdom of Saxony. After studying with local teachers, he moved to Venice where he completed his studies with G.B. Martini (Padre Martini) and Girolamo Pera. He was primarily known for his operas. It is now known that he also composed at least six string quartets. For many years, four of these, including the String Quartet in C Major were mistakenly attributed to Mozart based on the opinion of experts who examined unsigned manuscripts. It was not until 1932, that they were published as Mozart's Mailander or Milanese String Quartets. But in the 1960's the autograph manuscript to one of the so-called Milanese quartets was discovered in Padua, removing all doubt that this was a quartet by Schuster. Further research has uncovered references to the other three quartets clearly establishing that Schuster was the composer.
The String Quartet in C Major, formerly known as Milanese String Quartet No.3, along with the other three, date from 1780. It is in three movements: Moderato, Un poco Adagio and Allegretto. It is not hard to see how experts mistook this work for that of Mozart, who spent considerable time in Italy during this period, including writing works for the same patrons in Padua.