The IC-7300 is a transceiver where all heterodyning oscillators are derived from a single master oscillator.
This type of radio makes for very easy checking and calibration of frequency accuracy.
The video below demonstrates the technique.
The video used a local GPS disciplined source at 50.1MHz. The frequency was chosen to provide the greater resolution in setting the oscillator, though setting it to within 1 part in 50,000,000 or 0.02ppm is better than the stability of the oscillator (specification is 0.5ppm or 5Hz at 10MHz).
Any accurate known reference can be used, it could be WWV or the like, or even a MW broadcast station, though an accurate signal at 10MHz or higher is better.
The technique can be applied to the much older IC-7000, and many transceivers released since then, of various brands. The important thing is that ALL oscillators are derived from a single master oscillator.