I sucked the thumb on my left hand while focusing on the rotary log scale of my old flying watch, as illustrated at...
Always nice to touch-base with your horological collection, Andre. I go back periodically for a look-see, as would any admirer of precision tools.
-- don't try it at home, you'll go cross-eyed and give yourself a migraine
Andre, your dedication to Precision and Scientific Method is peerless.
All the best,
Dan.
