An M1 helmet with swivel bales, rear seam and textured paint. Bales are correct for period. 
I have just got these from Northern Thailand. The helmets are in a good, solid condition. Please see photos, as this is the one you will receive. I believe these are Vietnam war issue and then re-issued to the Thai army to replace their French Adrian helmets.
The helmet in this picture is the one you will receive. The photos form part of the description. Good for re-enactments and display.