Please, check the wiki.
And belittle the 1 AC all you want, it saves me millions on beefing up my heavy tank (literally)... Many are paying 500k+ per point of AC at this point... "just 1 AC? and it's not upgradable?!" It was free. You get what you pay for, and at times, you get what you don't pay for... In the sense of the latter, something > nothing. Enjoy it. ^_^
Furthermore, why does everyone seem to want to sell it? I've seen four complaints from people that couldn't sell it or trade it... Vet pride, much? =/