The theory, Wado-kaichin coins were issued all the way back in the era of Emperor Tenmu, was pretty much denied due to the discovery of a large amount of Fuhonsen coins, mentioned later.
和同開珎の発行を天武天皇の時代まで遡るとする学説もあったが、後述の富本銭の大量発見によってこの説はほぼ否定されている。