Eight months later, the dead CR2032 cell driving the “ruby” wearable LED has dropped to 2.15 V:
It’s not a true red LED with a 1.5-ish V forward drop, but a white / blue LED with red phosphor or a red filter, with a forward drop well over 3 V.
Against the sunlit backdrop from our kitchen window, the LED looks dark:
Seen in a dim room, it’s still glowing:
The current is now far below the 1 mA/div of my Tek A6302 Hall effect probe, so I have no way to measure the few microamps lighting the junction.