1st - I noticed this was your very first post - so, Welcome Aboard DeathCowOfEvil! You didn't list your state (or country) in your profile. So, you might consider jumping over to Sub-Forums: Select Your Area.... and selecting location information (i.e., clubs, hunts, finds, legends, maps, etc.) directly related to your state (or country). You might also consider adding your state (or country) to your displayed profile (SETTINGS -> EDIT PROFILE) so if you ask a question, etc. - people may have more success helping you (your location may help, etc.)...
2nd - I moved from What's It Worth? over to Forum: What Is It? for more exposure.
Nice M1917. Known as the Brodie helmet, these were first made by the Brits but the US started producing them also for use during WW1. Nice find to have an original unit marking on it. Any production lettering or marks on it? The Brits did produce the first 500k helmets we used I believe.