Concerto for Violin, Piano, and Orchestra (Mozart)

The Concerto for Violin, Piano and Orchestra, K. Anh. 56/315f by Wolfgang Amadeus Mozart is an unfinished work that was written in Mannheim in 1778. It was written for an "Academie des Amateurs" that was to take place in Mannheim. Mozart himself was to play the piano part and Ignaz Fränzl, the concertmaster of the Mannheim orchestra, was to play the solo violin part.
Mozart only wrote the first 120 bars of the first movement, and only the first 74 bars are completely scored. Alfred Einstein believed that the work was abandoned due to the disbanding of the Mannheim orchestra; however, that had happened earlier that year when the Elector moved to Munich and most of his orchestra followed him, so the "Academie des Amateurs" replaced the Mannheim orchestra. The most likely explanation for the concerto being abandoned is that Mozart left Mannheim in December 1778, perhaps because the "Academie" did not start as early as he thought it would. It is unknown why he did not continue working on the concerto on his journey home or when he was back in Salzburg.
References.
Mozart Jahrbuch 1991 p. 912