They just take their coupon/candidate of choice and deposit it into a box.
There are no pencils needed, no ambiguity. Ballots are hand-counted and totals are reached rapidly. A far less-hackable alternative to what exists in the US IMHO.
Problem back then was that people would literally beat you up on the way to the poll if they disagreed with your choice. It was an entirely different culture around voting, secret polls were not a thing.
I live in Oregon State and we are one of the few states that does all of our voting entirely by mail. I think it is the best way to do things. No need to go to the polls and you can do research while you fill out your ballot. We have polling offices available if you forget to fill it out on time.
I wasn't implying that voting coupons would still have the issue of people bullying you, just why we don't use that system anymore. And honestly coupons seem a little archaic to me, not to mention easy to manipulate.
I could argue that a system such as that is easier to have fraud simply because all of the tickets for a particular voter look exactly the same and there is noting unique on each ticket (the way it is marked) that can differentiate in a way to make fraud less likely.