Thank you Marcus. Never thought to look through your site for this.
So the antenna matches a Mustang antenna, especially the base. It has the round mast but tear drop base. The Fomoco cast markings and stamping on the antenna (#6 - 473) are present. But, the base gasket looks to be for a Cougar, and is marked C9WA. I have a package with the base cap and screws but the cap is not ink stamped. From your pics it is safe to say this looks top be a NOS Ford antenna, which is awesome. Now I just need to get the correct gasket to fit the fender and we will be good. My son is not in search of NOS parts for his Mach, but with "correct" repros around $95, he is pleased with this find.
Thanks to everyone for helping with this!