Hard to say after all these years if what you saw was a 1911, not a 1911A1, but it is not out of the realm of possibilities in 1971 to have a 60 year old firearm in an Army Reserve armory.
It was definitely a 1911, not an A1. No trigger area cutout.
As far as having a 60 year old weapon, this unit was so bad, in the event of DEFCON 1, pregnant women and children went before we did. I’m surprised we not have Sharps Calvary Carbines in the arms room.