As Steve says, it's certainly not a square dip, because the maker of this helmet is Gebruder Gnüchtel, Lauter/Sachsen. The square dips were produced by ET which stands for Eisenhüttenwerk Thale, Thale/Harz.
Nevertheless it's an attractive helmet, but as stated before, it's maybe a little bit to expensice for a standard M16...
Adler 1