Agin-Buryat Autonomous Okrug
Agin-Buryat Autonomous Okrug was a federal subject of the Russian Federation. On 1 March 2008, the region merged with Chita Oblast (which it was surrounded by) to form the new Zabaykalsky Krai.
Source: Wikipedia — Agin-Buryat Autonomous Okrug (CC BY-SA 4.0)