not without its flaws. The ventilator horns often let cold air in during the winter, requiring the wearer to block the vents with mud or fabric. The large, flared skirt tended to make it difficult for soldiers to hear, distorting surrounding sounds and creating an echo when the wearer spoke. Originally painted Feldgrau (field grey), the Stahlhelm was often camouflaged by troops in the field using mud, foliage, cloth covers, and paint. Official issue cloth covers in white and grey appeared in late 1916 and early 1917. Camouflage paint was not formally introduced until July 1918, when German Army Order II, No 91 366, signed by General Erich Ludendorff on 7 July 1918, outlined official standards for helmet camouflage. The order stipulated that helmets should be painted in several colours, separated by a finger-wide black line. The colours should be relevant to the season, such as using green, brown and ochre in summer. After the effectiveness of the M1916 design was validated during the 1916 campaigns, incremental improvements were subsequently made. The M1917 version saw improvements to the liner but was otherwise identical to the original design. M1918 Extensive redesigns were made for the M1918 model. A new two-piece chin strap was introduced and was attached directly to the helmet liner rather than the shell. Certain examples of the M1918 had cutouts in the rim along the sides of the helmet. It has incorrectly been said that these cutouts were to accommodate headphones while wearing the helmet. These cutouts were actually done to improve hearing and to reduce echo created by the large, flared skirt. The M1918 Stahlhelm can be distinguished from the M1916, as the M1918 shell lacks the chinstrap rivet on the lower side of the helmet skirt found on earlier models. Austro-Hungarian variants Austria-Hungary purchased about 416,000 German helmets from November 1916 until the end of the war and also began its own licensed production starting in May 1917. Around a million Stahlhelm of all variants were issued until the end of the war. Austrian M17 The Austrian M17 helmet was similar to the German M16 but was coloured golden-brown (known as Isonzo-braun), had a cloth chinstrap and had the chinstrap rivet located higher up on the steel shell. From May 1917 till the end of World War I 534,013 were produced, many of which were manufactured at the Krupp in Berndorf, Lower Austria. Other production locations