The markings look similar to what the 187th Airborne Regimental Combat Team used in Korea BUT.. their Tactical Markings were on the side of the helmet and not the front. Most of the liners were marked on the front 11th A/B. If this was a 187th TAC mark, this is for 3rd Battalion 187th.

I won't completely dismiss this as NOT being a 187th liner, but this is the first one I have ever seen if it were from the 187th.

I will have to do some more research and reach out to a friend of mine who has a large collection of 187th helmets..