Korean Ma Pae Four Horse Requisition Badge Bronze Joseon Dynasty.

Secret royal inspector, or Amhaeng-eosa (암행어사, 暗行御史, Ombudsman) was a temporary position unique to Joseon Dynasty, in which an undercover official directly appointed by the king was sent to local provinces to monitor government officials and look after the populace while traveling incognito. Unlike regular inspectors whose activities under Office of Inspector General were official and public, the appointment and activities of secret royal inspectors were kept strictly secret throughout the mission.

For their secret mission, they received a letter of appointment (bongseo, 봉서), a description of their destination and mission (samok, 사목), and "horse requisition tablet" called mapae(마패), which they used to requisite horses and men from a local station run by the central government.