Yes, they are seldom seen. While I have a number of them from fullsize Chevies, all found in owners manual packets, the one from that 69Z is the first one I have seen actually found inside the car. Sometimes you just get lucky. When taking apart a car with the original carpet, you really have to check all spots under it.
Anyway, here is one from a 68 St. Louis built Impala. Again, the one from that 69Z is a different form that the ones I have. I'm sure there were a number of variations between the plants.