Translation:
Around 30,000 of these helmets (in sizes 60 to 68) were produced by Thale's Eisenhuttenwerke, and therefore all bear the ET label. They were field tested by the Storm-Battalion Nr5 Rohr in late December 1915, with the first batch of 30,000 helmets being released in late January 1916. Interestingly, they were not designated M15, but I assume that this is because it was an "unofficial production headset" until testing was completed. These helmets can rightfully claim to be the very first mass-produced German steel helmets in the 20th century.
However, the pronounced downward curvature of the front visor towards the rear of the helmet proved problematic in the design, with many helmets known to be prone to stress cracking in this particular area. In fact, Ludwig Baer states that all the examples studied while writing his book "The German Steel Helmet - 1916-1918", had cracks in the area where the lateral transition is located. Production was therefore stopped and the new helmet was produced with a much smoother transition from early 1916. Due to such a short production period and many potentially destroyed examples, they are now very rare, but it is evident that they were used until the end of the First World War, as examples of camouflage from the "1918 Directive" period are still encountered today.