Sorry Greg, I prefer my helmets untouched as much as possible so that is why I don't advise on paint removal or such. M18's are in my book in the original green, and the repaint which was performed in the 40's denotes this by naming them M18-40. If you want to open this discussion that is fine, but as far as I know this is the way these lids are named pretty much everwhere.

Ray, out.