There is no record of an act that prohibits shichusen (counterfeit money) just after the issue of Fuhonsen coin, and such act was first established only after the issue of Wado-kaichin, which means shichusen was allowed if Fuhonsen coin was circulating money.
富本銭発行直後に贋金（私鋳銭）を禁じる法令が出されたとする記録がなく、その最初の例が和同開珎発行後であること（もし、富本銭が流通貨幣ならば、贋金の存在を放置していたことになる）。