You'd have to hide the results of the vote if you're collating them with timestamp, otherwise you could pretty easily figure out Bob who showed up early voted f

You'd have to hide the results of the vote if you're collating them with timestamp, otherwise you could pretty easily figure out Bob who showed up early voted for the square. And I'm unsure how adding timestamp helps with the problem you're trying to solve, don't you just need Sum(machine vote count at location X) == voters visiting location X. (Also this hueristic is kinda leaky since how do you account for voters protesting with intentional spoilers?)