Recently, archaeologists found a mouth harp in Cheremshanka, south-central Russia, approximating that the ancient instrument is approximately 1,700 years old. However, much to the surprise to the scientists who found the mouth harp, the instrument was still in working order and could still be played over a century later.
The working instrument was one of five antique mouth harps found in the region. As explained in a National Geographic article,
The instruments were likely made by craftsmen from the splintered ribs of cows or horses, and they are thought to date back 1,700 years to the period when the Huns and their descendants controlled much of central Asia. The tribes who populated the region at the time were nomadic, spreading across central Asia through modern-day Mongolia, Kazakhstan, northeast China, and southern Russia. The mouth harp that [was] played is about 4.3 inches long and 3.3 inches wide.
As noted by Andrey Borodovsky, a professor at the Russian Academy of Sciences’ Institute of Archaeology and Ethnography who used the instrument, when played, the mouth harp sounds like flageolet, a flute-like instrument that was popular during the Renaissance.
 [H/T National Geographic]