Well, I measured the stock against my other A1 original, non trap-door stock and they are the same length........9 7/8" from the back of the buttplate to the receiver. So, I was mistaken in my description and it would appear to be an A1....not an A2. To be honest, not being an "afficianado" of the M16/AR15, I didn't know there was a difference in length but obviously there is. I assumed it was material and design that made the difference.
I'll ammend my post to reflect that it is an A1 stock with the trapdoor, not an A2.
Thanks for asking. If you're still interested, let me know.