This helmet is a "Casque Troupes Toutes Armes Modèle 51 OTAN" made by Dunois & Fils de Vincennes in 1962.
This is an example of a type 3 shell. It has fixed bails but the shape of the bails is different then the type 1.
I haven't found any further information about Dunois.
For pictures of the liner that came with this helmet see part 2 the liner