xxx: I don’t want to seem boring, but then what was the triple perfocard?
Are the holes triangular?

A triple perfocard should be made from two, where the first is made holes (ordinary, square) for 1 and -1, 0 - no holes. A second light filter or resistor that reduces the voltage by half. It makes holes for 1 and not for 1. Thus, a hole is = 1, a half hole = -1, no hole is = 0.