Rassah: put it in the freezer in the kitchen and collected data while it was cooling down. There was still plenty at 0ºC, but it smoothly went down to zero entropy around -20º. The cells with high skew are those which effectively constitute device signature.

Rassah: Yes. If you plug tis device into your PC while holding down the button, it shows up in "flash mode", where instead of just a USB stick with a JPG on it, you get to see all the system and settings files. One of those files is a user provded sald (like diceware) that will be combined with the rest of the entropy sources to produce the final key