A tweet from 2016 or so referencing a longer writeup I made: https://www.gwern.net/Statistical-notes#proposal-hand-counti... My idea was that CNNs were good enough that you didn't have to use hacks like QR-codes or specially-designed papers; I think that someone has already done something equivalent, unless I'm thinking of you guys! (Even if you did go to CNNs for pure hand-counting, it's an obvious enough idea I doubt you got it from me, and in any case, it's implementation that counts.)