As mentioned in the section of 'History,' there are indecisive three theories over the issue concerning the production age of these statues: the first theory suggests that these statues had already been completed by 688, the second theory suggests that they were produced in 697 because there is a record in "Nihonshoki" that Kaigan-hoe (ceremony of "Kaigan", enshrining newly built Buddhist image and to put a spirit as opening eyes to Buddhism) was held at Yakushi-ji Temple in 697, and the third theory suggests that these statues were newly produced after the relocation to Heijo-kyo.
制作年代については、「歴史」の項で述べたように持統天皇2年（688年）には完成していたとする説、『日本書紀』に持統天皇11年（697年）、薬師寺にて仏像の開眼法会を行った旨の記録があることから、この時に制作されたとする説、平城京移転後の新造とする説があり、決着をみていない。