Knife Money (Mingdaoqian) is a bronze coin widely circulated from the late Spring and Autumn Period to the Warring States Period. The coin bears the character "Ming (明)" on one side and three straight lines on the handle with the ring-shaped end. Similar coins unearthed in the northwestern part of the Korean Peninsula, including the Cheongcheongang River, the Daedonggang River, and the upstream of the Yalu River. Mingdaoqian is the most frequently found among the ancient Chinese coins in the Korean Peninsula, indicating that Gojoseon engaged in active trade with the Yan Dynasty.