W.W.I.: 1917. Postal cover with a complete commemorative stamp set from 1914 commemorating the 6th anniversary of assassination of the Austrian Crown Prince and his wife in Bosnia.

First Day – Cancellation in red ( scarcer variety ).

Franz Ferdinand, Archduke of Austria-Este (December 18, 1863 – June 28, 1914) was an Archduke of Austria, Prince Imperial of Austria, Prince Royal of Hungary and Bohemia, and from 1896 until his death, heir presumptive to the Austro-Hungarian throne.

His assassination in Sarajevo precipitated the Austrian declaration of war. This caused countries allied with Austria-Hungary (the Central Powers) and countries allied with Serbia (the Entente Powers) to declare war on each other, starting World War I.