Not only Shichusen, but wartime coins of the Chinese Southern Sung Dynasty and Minsen (bronze coins produced during Ming Dynasty) mingled with poor quality coins and were usually of poor quality, therefore they were collectively called akusen.
そうした私鋳銭ばかりでなく南宋の戦時貨や明銭自体も不良銭が混じるなど品質劣悪なものが普通だったため、これらを総称して「悪銭」といった。