What does "HF-QUARTZ 4.19 MHz" on a ~1980s wall clock mean?

Question

I have a wall clock from the 1980s or early 1990s. Probably 1980s. It has a black box behind/"inside" it which powers the whole thing. It's made by Quartz.

On the black box, it says "HF-QUARTZ 4.19 MHz". What do they mean by "HF" and "4.19 MHz"? Does it use radio signals? Can it be told to keep the time automatically by using radio signals at 4.19 MHz? Is that some kind of time-sync radio frequency?

I found no button to press to activate its "auto-time-keeping" feature, if such a thing exists. I first thought that a little black button might be it, but it doesn't seem to be a button after all. It only has "on/off" (called start/stop) and a little wheel you use to manually set the time, mechanically. And a battery, of course.

Does this mean something completely different? Why mention a number of megahertz at all for a wall clock? What kind of significance does it have? Why does the user need to know that it uses "4.19 MHz" for something? What is that something?

Answer 1

Can it be told to keep the time automatically by using radio signals at 4.19 MHz? Is that some kind of time-sync radio frequency?

I'm not aware of any timekeeping signals broadcasting on 4.19 MHz. However, web searching for "4.19 MHz" turned up a number of mentions of clocks whose timekeeping oscillators used a 4.19 MHz quartz crystal (as opposed to the more usual 32.768 kHz), and that this might be a more accurate (for its time) mechanism.

This also explains why they brand it "HF-QUARTZ" — it's the quartz that's high frequency.

Why mention a number of megahertz at all for a wall clock? What kind of significance does it have? Why does the user need to know that it uses "4.19 MHz" for something?

Advertising! "Our clock is SUPER HIGH TECH and therefore better."

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I found no button to press to activate its "auto-time-keeping" feature, if such a thing exists. I first thought that a little black button might be it, but it doesn't seem to be a button after all.

I'm pretty sure this isn't a radio controlled clock, but if it were, I expect there would not be a button to activate it. Rather, such clocks do so automatically; for clocks using the WWVB 60 kHz signal, usually at night when signal propagation is better. There could be a switch to disable the radio timekeeping but it would likely be a slider rather than a pushbutton.