Any historical significance to the rifles Gibbs converts was gone when the bolts were welded shut and the magazine disconnecter was welded closed. Those are former drill rifles Gibbs is turning back in to shooters.
They also don't make A4s out of all of them, they sell A3s as well.
I've yet to find anything that says that all of the gibbs guns are drill rifle rescue jobs. I also see nothing that says that the AIM rifles are Gibbs.
the only gibbs non-A4geries I've seen are camo painted and hold no value at all despite being priced comparably with a USGI condition rifle.