My grandfather brought a few items back from his time in Europe and I was fortunate enough to inherit some of them. One was a German helmet that I originally thought was a proper WWII helmet, but I brought it back from my parents a few years ago and noticed it was actually a WWI model!
With a metal frame, it would be an M1917. There were no leather supports when I got it (so I'm guessing it was never used) and the metal frame had unfortunately rusted from years in my grandfather's garage but I was able to get a nice reproduction and a chin strap from the Prairie Flower Leather Company. The inside of the shell is stamped Si66, which would make it a size 66 from the manufacturer below:
Si. - Eisenhütte Silesia, Paruschowitz Oberschlesien - (sizes 62, 66 shells)
So I figured it was about time I got around to sharing!