Tsellati, on post #5 you can clearly see the Army weave pattern were the Marine Corps buttons are ... I think the wear of your coat is misleading you as it's sometimes difficult to see the special weave but if you compare to a sage green USMC coat, you'll see the difference and there will be no doubt 
Son-of-a-gun, you're right. Now I see the Army HBT weave once you pointed it out to me. The worn/aged appearance of the rest of the shirt certainly does not make it easy to discern the pattern.
On another note, I wish it were my coat, but alas, it is not. It's actually being auctioned on eBay and it appears enough other collectors (more educated than I regarding USMC camo shirts) pegged this one for being original as it's up to $160 with another 2+ days to go. It's just too steep for me now.
Tim
Edited by tsellati, 16 August 2012 - 06:10 PM.