Punch card operated padlock
As you can see, it's operated by inserting the plastic card and pushing the card in slightly. I believe it works similar to a pin tumbler, as you can see the tops of plastic "cones" in the slot. I'm guessing these act like keypins, and the size/position of the holes on the card determines if they line up correctly. If all lines up, the lock mechanism will slide to the left and retract the latch.
I'd like to find another and dissect it, as this one was one of the original locks in my collection 20 some years ago!
Also came with a smaller keycard, but it's lost at the moment.