I know there has been heavy debate in the past on what book is truly the first appearance of Phil Couslon, and the context of that appearance, but now it seems CGC has modified their labels to reflect their stance on it (see below.)
It seems Coulson is in the same boat as Harley Quinn, with both characters having "first" appearances in comics that are movie or TV show tie-ins, and then years later finally have a "first" appearance in their respective regular comic universes. I'm not sure what the print run is on the Wal-mart Custom Comic, but it only came in certain Iron Man DVD bundles that Wal-mart sold in late 2008, and so far on the census, there's only my two universal 9.8 copies that I just got back, and two 9.8 Sig Series books.