5 Kings that ruled Greece

 George I, Constantine I, Alexander, George II, and Paul. I'm unsure of what exactly this stamp commemorates, perhaps the fact that George I began his reign 100 years prior to this stamps issuance which coincides with Paul becoming gravely ill and someone wanted Paul honored on a stamp and this 5 King tribute was subtler. Paul died in March of 1964.
 The story of coups, exiles and ascendancies is rather a soap opera. George I held reign for 50 years, which is the longest reign of any King in the history of Greece.

                

JimmyB

We Three Kings

 Karl II, Ferdinand I and Karl I appeared on this stamp issued Nov. 1, 1931 commemorating the 50th anniversary of it's elevation to Kingdom from Principality. Romania's independence from the Ottoman Empire was recognized in 1878 by the Treaty of Berlin.
 As to why and how the two Karls got on this stamp I have no clue. If your interests include Coat of Arms, they appear to border the vertical edges. This stamp was also printed in a 10 Lei value of a blue color vs this blue green hue. Also the 10 Lei stamp had the years 1881 and 1931 appearing in the dark rectangles on the bottom left and right of the portrait. Someone must have forgotten to put the dates on the 16 Lei issue.  

JimmyB

Chinese Mantis

 Tenodera aridifolia sinensis, is one bad mantis. Found in China and surrounding islands, it was accidently released in the U.S.. This mantis has been documented eating hummingbirds. Yes, it has been known to eat BIRDS!!!!

   
 Released in June of 92, this is the largest (2 Yen) stamp in a set of 4 different insects.