The Modèle 1951 was designed to have the same general shape as the US M1 Helmet, in an effort towards standardisation within NATO. The two differ in that the M1 has a longer visor and a more pronounced downwards slope on the sides. The Modèle 1951 comprised a heavy external cover, made of 1.2 mm of an amagnetic alloy of manganese steel, and a lighter inner helmet. The Modèle 1951 was produced until 1976, before being superseded by the Modèle 1978 helmet. It nonetheless remained in service well into the 1980s.