The first mourning issue in the world.
Opinions differ on what the first stamp in the world was to commemorate someone. But it was definately a US stamp.
Opinions are various on the world’s first mourning stamp, but it is sure that America has got the scoop !
In June 1866, a 15 c (black) stamp with the portray of Lincoln was issued in America. That president, though, got killed on April 14, 1865.
The fact that the stamp was issued in black as a mourning stamp is quite unlikely, because it came into circulation almost one year later and there is no post document clearly stating that is was a mourning stamp.
As a first official mourning stamp, a 2 c stamp is mentioned, which appeared on September 1, 1923 in the US, printed in black and it had the portray of the deceased president Warren Harding.
There is also an interesting variety of this stamp, namely a horizontal couple which is not vertically perforated.
The second official mourning issue is one by the USSR, with portray stamps of Lenin.