After seeing the wonderful posts on lapel pins made by Joe (Jmar) I was prompted to dig around and pull out one of mine.
This lapel pin is a simple AEF overseas chevron version, the pictured example with one chevron to denote the veteran served for one six month period of overseas duty. I have seen one, two, and three chevron versions of these pins. I do not know if they ever made them with four or more chevrons, if anyone does then let me know.
If anyone has the other versions please feel free to post them here.