An unpublished and undocumented autograph working sketch-leaf for two realisations of violin sonatas by Antonio Vivaldi, by the supreme Russian violinist Nathan Milstein. Undated, one page (recto/verso) of 40 bars in blue ballpoint pen and pencil. The 5 bars in pen relate to the fourth movement Giga (Allegro) of Vivaldi's Sonata in D minor Op. 2 no. 3, whilst the 35 bars in pencil relate to another unidentified Sonata for Violin and Piano by Vivaldi (most likely a Grave movement or Sarabande). Although Milstein composed original works and arranged music by other composers, it is not documented that he realised any sonatas by Antonio Vivaldi. A particularly rare and important manuscript. In overall fine condition.