Four characters surround the hole, read as 寛永通寶 Kan`eitsūhō (寛永通宝 for present day lettering) 永 (Ei) with irregular font, called `Nisuiei`
Obverse script
Obverse lettering
寛 寶 通 永 (Translation: Kan`ei Currency)
Reverse description
Blank.
Reverse script
Reverse lettering
Edge
Mint
Mintage
ND (1626) - マ頭通 MATŌTSŪ; マ as head of 通; 用 in 通 has long right leg - ND (1626) - 正三刮去; 寛 with short left leg; high 通; same as true 三 reverse, but 三 removed - ND (1626) - 濶縁 KATSUEN; thick rim; high 通 with large space between dot and コ - ND (1626) - 短寶 TANHŌ; low 通; space between short 寶 and inner rim - ND (1626) - 長字 CHŌJI; マ as head of 通; 用 in 通 has long middle leg - ND (1636) - 背星刮去 HAI-HOSHI KAKKYO; low 通; Same as dot reverse, but dot removed -