Its Achille’s heel in terms of accuracy is the plain crystal oscillator it uses as a frequency ... the “VC” part — and the tiny PCB tucks inside the case near the battery compartment.

[Paul] likes a precise oscillator. His recent video shows a crystal oscillator with a “watch crystal” and a CMOS counter, the CD4060. Using such a circuit can produce very stable frequencies ...

An oscillator that uses a quartz crystal to generate a frequency. Such devices generally output a fixed frequency, but some can be controlled by a tuning voltage over a small range. Contrast with VCO.