I know Besset worked on Diatto, Berliet, Hispano-Suiza, Peugeot, Genestin, Delage, Rolland-Pilain, Talbot, Voisin Farman and Bugatti...no mention of a Latil in my sources.
Since I was looking for a Latil Limousine by a particular coachbuilder, when I found that pic I took for granted that it was his...but as you said, there's no mention of the coachbuilder with the pic, so I may be wrong...how do you support your guess?