This is a genuine, complete but rough condition US M1917A1 helmet.
Also known as a the "Kelly Helmet", these were adopted in the years leading up to WW2. They featured a improved suspension over the original 1917 helmets. This one is especially unusual - instead of using a WW1 American or new production shell from the 1930's, this 1917A1 was made with a British WW1 production MkI shell. Helmet shell can be denoted as British manufacture by the overlapping seam on the rim, and interestingly enough the chinstrap bales have been replaced with American made examples.
Helmet is complete, but the leather liner is in rough condition. Chinstrap is present and has signs of wear and use. Finish on the shell is nice and untouched, though paint is missing and there are dings and scuffs on it. Seems to be a few small spots of a white paint on it. Additionally, it has a few large dents on the top.
Steel shell lot code is HS163. Additionally, D111 has been ink stamped on the inside rim of the helmet.
A rarely seen helmet, this would look great in a WW2 American helmet collection.