HP48 Clock Variableness

[Dave Shaffer]

Yes, those VCRs almost certainly used the 60 power line as the clock reference. In the long run, as you discovered, it is pretty good - the power company can diddle the frequency so the total number of cycles over time is correct.

Here's some more info on the 32768 crystals as used in watches: https://tf.nist.gov/general/pdf/2276.pdf