Lest you think (as I did) that the first time was an anomaly or random:
And with a second system / measurement device (this one more accurate - the Firstbeat Bodyguard used with their Lifestyle Assessment), still showing a vastly increased HRV from my usual numbers:
My resting pulse was also 37 that night, which is pretty low even for me.
Next up I am thinking I will do a 60 hour fast, so eat dinner on Monday night then break the fast on Thursday morning instead of Wednesday (as I did in these last two).