Other production locations included:  The Hungarian M18 variant was similar to the Austrian M17 design, but the chinstrap rivet was smaller in size and located even higher up than the Austrian version. It was colored in golden-brown (known as Isonzo-braun). These were manufactured at the Krupp in Berndorf, Lower Austria. There was also a quite different, domestically developed Berndorfer variant. 139,968 were produced from May till November 1917 at the Krupp in Berndorf, Lower Austria  The formation in 1917 by the Ottoman Empire of stormtrooper battalions following the German model prompted the requirement for steel helmets, as these had not previously been adopted. Although German helmets were ordered, Ottoman officers believed that the design impeded the soldiers' ability to hear orders in the field and requested that the visor, ear and neck protectors be removed, which was done using grinding machines. Germany delivered 5,400 visorless versions of the M1918 helmet for the Ottoman Empire. The missing front visor was thought by the Germans to be for religious reasons, and it was claimed that it was to allow Turkish soldiers to touch their foreheads to the ground during prayer, without removing their helmets. However, this story has been disputed. The Turks rejected any more than the 5,400 delivered and an unknown number from the overrun were issued to German armed forces and were used by German Freikorps units after the war. In 1932 the Army High Command ordered the testing of a new prototype helmet intended to replace the older models. It was made entirely from a composite plastic material called "Vulkanfiber". The Model 1933 Vulkanfiber helmet kept the basic form of previous helmets, but was much lighter. It was put into limited production following favourable field tests in early 1933 and small numbers were issued to Reichswehr infantry, artillery and communications units. It was removed from service following the introduction of the M1935 helmet and most of the remaining stock were reissued to civil organizations such as fire brigades and police forces. Some examples were also retained for parade use by senior officers, who were not generally issued with the "Stahlhelm". In 1934 tests began on an improved "Stahlhelm", whose design was a development of World War I models. The Eisenhüttenwerke company of Thale carried out prototype design and testing, with Dr. Friedrich Schwerd once again taking a hand. The new helmet was pressed from sheets of molybdenum steel in several stages.