I have probably had these for close to 40 years and totally forgot about them until I came across them today, looking for something else. This seems like a good place to find out what they really are.
The tax stamps without serial numbers were represented as "proofs" and the others as "color varieties". I have no idea whether this is accurate, but I haven't seen multiples or a full pane like this elsewhere.
Can anyone shed light on these? Is there much of a market for them?