A 13th century manuscript of the cycle of Guiron le Courtois, which belonged to the Rotschild collection and was lost about fifty years ago, turns out now in a series of photographs. The importance of this evidence can be appreciated both for its content, for the language used by the copyists, and moreover for the exceptional series of illustrations, which helps to estimate the origin of it in Milan during the Visconti time. A first analysis of the manuscript was carried out by members of the "Guiron Group", and the results of it will be presented at the University of Lausanne on 22-23 February 2013 (http://www2.unil.ch/lombardy/conferences.html#a).