Here's what happened. Sometime during the last 44 years, the original factory installed electric antenna stopped working or the mast broke off. The owner, being a cheap bastard, saw the price of a replacement factory electric antenna and opted to replace the factory electric with a $7 manual antenna from the local auto parts store. Doesn't really matter when your '72 Z was manufactured, it came with an electric antenna and a control switch to raise and lower it on the original factory radio face plate. Sounds like you also have an aftermarket radio and faceplate so the antenna switch is long gone.
Did you notice the electrical wiring for the original antenna in the space next to the radio speaker?
Dennis