FDC #5: Wildlife Series "Ducks", Pakistan

Another beautiful FDC from Pakistan is here to give a treat to your eyes. A set of 4 Pakistan stamps was issued featuring water birds of Pakistan. These birds included:

• Mallard (Anas Platyrthynchos)
• Gadwall (Anas Strepera)
• Greylag Goose (Anser Anser)
• Common Shelduck (Tadorna Tadorna) - Also featured on the FDC

The Stamps were issued on 31 December 1992. They are really beautiful and a feast for the eyes. They were issued in a strange way as the sheet contained 16 stamps. 

The stamps were placed at different places in each row but the rainbow on top remained the same, which meant that all 16 stamps are unique. You can see a scan of the stamp sheet. I think that it is very rare to issue some stamps like this. Are there any other such examples or have you seen any such example anywhere in the world???

If you remove the stamp of "Common Shelduck (Tadorna Tadorna)" from every row then you can make a complete rainbow on top using these four stamps. Same is the case with other three ducks.