Thanks for the explanation BPC, I didn't know that. In Argentina score cards are usually not perforated (at least in amateur rounds and championships). We literally exchange cards with other competitor before the start (if playing with caddies, player A's caddie keeps track of player B's card and viceversa), so we often only keep written track of the the rival's score. That's a bad practice. All I've read about Augusta 1968's incident mentioned a single score card kept by Tommy Aaron and signed by De Vicenzo so I thought they did the same at that time.