Here is my Big Red One M1917 helmet. I really don’t know much about it, and wanted to see if anybody knew more about these than me. I took a picture of the heat stamp which is "ZC193" to give more info(The picture on top has the heat stamp circled as well). It obviously has no liner, as you can tell from the pictures. If anybody could put a value on it, that would be much appreciated. Please note, I am not selling it, I just want to see how much it’s worth