M1 helmet heat stamp

[2ndRangersWW2]

Hello everyone, I recently got my hands on yet another M1 helmet. It was listed as a Vietnam era helmet however I am confused on the heat stamp. The heat stamp falls more in line with wwii era McCord helmets. Being 4 numbers followed by a letter. The confusing lies with either it being a McCord one from late wwii, or an Ingersoll from Vietnam. Ingersoll tended to label the stamp as " I-0000". The letter i Followed by 4 letters. There is no letter at the end of the stamp. And yet again I am confused on the stamp as i cannot tell if it is a letter "i" or 1. The wwii ones are a distinct 1, and the one on mine looks more like the letter.
Let me know what you guys think. The reason I did not add the other manufacturers of the helmet durning Vietnam is because they don't remotely look like the one I have.

[Tank Destroyer]

It’s 1227B, it’s a WW2 McCord

[2ndRangersWW2]

I appreciate it! That was what I was thinking as well