Fiberglass Stock

I need some help from you guys identifying a stock. I have one for sale in our classifieds forum with pictures and the numbers molded inside the stock. Some people have asked me if it is a USGI stock, what kind it is, and if it was brown originally. I am new to the M1A forum and do not know how to tell if it is a true USGI stock or not. Can someone tell me how to find out or look at it and tell me about it. I really want to represent it correctly when people ask about it. You can post it here or IM me with any information and it would be greatly appreciated. The green fiberglass has numbers on the inside, they read as follows:
D-3741
GB-1
DT


http://m14forum.com/px/96324-m14-stocks.html