This violin sonata is not listed in Köchel catalog. The source is "A favorite SONATA for the Piano Forte or Harpsichord, with an accompaniment for a Violin. Composed by W. A. Mozart" published by J.Bland in London. The edition has no dating but not earlier than 1780. Such later publishing may deny the authenticity of this music by Mozart.
:? Mozart's Violin Sonata in D K6.deestAllegro
RONDO GraziosoInstruments; CH1: Violino, CH2: Pianoforte, Source; NMA: X/29/2 p.177

