1921. "Royal Consulate of the Kingdom of Serbs, Croats and Slovenes, Constantinople", registered envelope to an address in Belgrade, correctly franked 15 pi and paid with 7 1/2 pi bistre (horizontal pair) of Surcharge on stamps of King George V, tied by a fine strike of large double-circle "BRITISH POST OFFICE CONSTANTINOPLE / C / 5 SP 21" in black, blue/white "R" label adjacent, at reverse another strike of despatching postmark, BELGRADE arrial and Splendid sender's red wax seal. (Image)