Manuscript, in ink, in the hand of Muzio Clementi.
Most likely transcribed from the first ed. of full score (London : Cianchettini & Sperati, ca. 1810)
At bottom of p. 1: "This is one of the immortal Mozart's stupendous compositions, also this score written by the illustrious Muzio Clementi & now in the possession of J.B. Cramer."