It the same way as Heijokyo was a developed form of Fujiwarakyo of the Emperor Jito's period, Wado Kaichin was also a developed form of Fuhonsen coins and also followed the example of Tang coinage.
平城京が持統天皇期の藤原京の発展形であったのと同様、和同開珎もまた富本銭の発展形であり、また唐の銭貨にならったものであった。