500 Tenge Eagle owl head, crystal eye

Kazakhstan's National Bank produced a series of wildlife-themed gold issues in the early 2010s celebrating species native to the Eurasian steppe and its surrounding ecosystems. The eagle owl — Bubo bubo, the largest owl species on earth — has a documented range across Kazakhstan's vast territory, from the Tian Shan foothills to the northern grasslands. The embedded diamond serving as the eye was a deliberate production choice, not ornamental excess: the series was explicitly positioned for the international collector bullion-plus-gemstone market that several post-Soviet mints were aggressively targeting at the time.