Most likely postwar repainted M40 Combat Helmet (Stahlhelm M40). The stamped sheet steel construction M40 helmet is showing a most likely postwar blue-grey overpaint, see photos.  All three liner retaining rivets are intact. The interior of the helmet is a slightly damaged M31 leather liner. The shell is marked with maker and size 'EF66'. 'EF' is indicating production by the 'Emaillerwerke AG' from Fulda. The reverse interior neck guard apron has a stamped lot-number '4890'. Based on the lot number it will most likely be a Heeres helmet or SS helmet. Priced accordingly!