IECS = Improved Environmental Clothing System, after searching it appears IECS is the older OD items. The new CADPAT items are ICE/Integrated Clothing Ensemble
Anyways, the jacket I was referring to is the CADPAT combat jacket, has a zipper and buttons along the front, and a zipper along the bottom so you can stuff the jacket into it self.
http://i43.photobucket.com/albums/e390/edstorey/Untitled-1.jpg here's a picture I found of it
If there is confusion with your kit list, I'd recommend checking with your chain of command to confirm what is what.