I have this miniature sheet from Nigeria, 1986 insects. There are some curious perfs on the two right-hand stamps. I wondered if it is a perf error or variety or something? Probably something pretty common, but I'd love to hear your thoughts...
Yup, you got an error. Looks like it was fed into perf machine one too many times. Don't know how rare. Don't sell until you know more. Try Googleing to see if anyone is selling. Try FeeBay to see what activity there is on this item.
If You find many offers to this item to sell, it will give a hint at what it might be worth. No leads at all, then it 's not common and probably worth a lot.
I had a Great Britain MH16 color missing error (Greenish Blue), that Scott's said was worth $100 MNH. So I checked FeeBay and found a used one that sold for $265+. I guess that is about the only thing FeeBay is good for.
Many thanks for your response and useful information. I've done a bit of digging and found similar items but nothing exactly the same. As you suggest, I will hang on to it and keep researching - it may even end up in my own collection!
Your missing colour error was very interesting - it's amazing what we find sometimes.
