Principality of Bulgaria
After the Russo-Turkish War of 1877-1878, the 1878 Treaty of Berlin set up an autonomous state, the Principality of Bulgaria, within the Ottoman Empire. Although remaining under Ottoman sovereignty, it functioned independently, taking Alexander of Battenberg as its first prince in 1879. In 1885 Alexander took control of the still-Ottoman Eastern Rumelia, officially under a personal union. Following Prince Alexander's abdication (1886), a Bulgarian Assembly elected Ferdinand I as prince in 1887.
The new country introduced its own coinage in 1881, displaying the legend "Principality of Bulgaria"; as a nominal vassal of the Ottoman sultan, the monarch of Bulgaria was styled as a Prince.
Full independence from Ottoman control was declared in 1908, whereupon the monarch became a Tsar (king) and the country became ЦАРСТВО БЪЛГАРИЯ.