This could also be an example of the Model 1915 private purchase helmet that came with M91 side posts. It originally had special chin scales which fit on to the side posts. In this case we have a helmet fitted with an OR's leather chin strap. Does the spike un screw? There is also a special M15 spike associated with these which twists off like the OR M15 helmets. This has Awes top quality liner in it with the threaded sweat band. Awes also stamped their name on the inside of their spike bases. This was a premium quality helme when purchased.