What are quartz crystal oscillators?
Quartz crystal is not the same thing as crystal oscillator.

Quartz crystal consists of real physical crystal that has precise dimensions. The higher the desired frequency, the smaller the crystal must be. So it is practical to make them only in certain range (common values are 4 MHz - 40 MHz, and then low-frequency 32 kHz for RTCs).

It works by piezoelectric principle. Applied voltage causes it to contract and vice versa. At certain frequency, it gets into mechanical resonance which is projected into electrical resonance.

Quartz crystal oscillator is circuit that contains a quartz crystal and produces periodic signal. It can be integrated or constructed from individual components. One example is single-inverter oscillator.



The part numbers you provided are almost certainly form an 4MHz crystal.