Most anything that "flashes 12:00" is going to be using a crystal
timebase and not care about power line frequency. They flash 12:00 since
when they loose power they need to have the time set again, not anything
to do with line frequency.

Ah, no...

Anyone who has a device with a crystal oscillator timebase knows that
the device has to be reset to the correct time occasionally. On the
other hand, plug-in devices that use the 60 Hz signal for the timebase
have been (up until now) essentially perfect since the signal has been
manually twiddled to make it so. (There is actually a 10 second
tolerance in the East, less in the West.) And implementation is dirt
cheap: you capacitively couple to the power line, use a Schmitt
trigger, and some divide-by-60 counters. With better performance at
less cost, using the power-line frequency as a reference is the
preferred method.

Thing become ambiguous in plug-in devices with "battery backup."
These devices do have crystal oscillators to ride out the power
outage. When the power is on they can either use the crystal
oscillator as reference, or the power line as reference, however the
device was designed.

- Jonathan