Treatise on Painting by Leonardo da Vinci, manuscript

Treatise on Painting by Leonardo da Vinci  (E.II.6)

An apograph manuscript of the Treatise on Painting by Leonardo da Vinci was purchased on October 25th 1940 from the Hoepli Antique Bookshop of Milan. Held by the Raccolta Vinciana, the apograph was the subject of an essay by Carlo Pedretti published in 1959 (C. Pedretti, A New Apograph of the "Treatise on Painting" by Leonardo da Vinci, in Bibliothèque d’Humanisme et Renaissance, Tome XXI, Librairie E. Droz, Genève, 1959, p. 446-50), that stemmed from the fact that the manuscript, unlike the other apograph held by the Collection, had not been included by Steinitz in her bibliography: being instead erroneously recorded in the library catalogue as not relevant.   
The writing of the manuscript is uniform, from beginning to end, but small corrections to the text in another hand or probably either by another pen or using different ink were carried out, denoting checks made from a more correct source.
It is reasonable to assume that the compiler had borrowed from sources that preceded the editio princeps, but that the drafting of the manuscript may have occurred at a later period.