Suanpans (Chinese abacuses) and sorobans (Japanese abacuses) are bead-and-rod calculating tools that descend from a common ancestor dating to the Han dynasty (206 BC–220 AD). The suanpan uses a 2:5 bead design adopted during the Ming and Qing dynasties (1368–1912), while the soroban simplified this to a 1:4 bead design during Japan’s Muromachi period, matching…