You have assumed the radio was "perfectly tuned" from the factory.
A fair assumption today, but a less than fair assumption in the yesteryear and depending on the brand.
You ave assumed that the radio has not drifted from its factory tune since it came off the line.
Also a fair assumption today, but certainly not a very good assumption for a older radio been subjected to vibration and heat/cool cycles.
It is not fair to ask some one to draw conclusions, when you don't state the assumptions.