French Helmet "Casque Troupes Toutes Armes Modèle 51 OTAN" or "TTA 51"
After world war 2 the French came up with their own US M1 clone.
It looks a lot like the US M1 but the shape of the shell is different. The US M1 liner will not fit into the TTA 51.
This TTA 51 is a type 2, it has swivel bails to hold the chin strap. The type 1 has fixed bails like the first US M1 helmets.
My helmet is made in 1953 by S.A.U.F. Paris. I haven't found any information about this company.
For a lot of additional information about this helmet see world war helmets Mle 51 TTA
SAUF Paris 1953