On the other hand, because of the fact that no mirror similar to the Sankakubuchi Shinjukyo Mirror was ever discovered in China and that some mirrors had the name of eras already changed in China or had nonexistent eras, there are theories that they were made in Japan or produced by the craftsmen that came from China, or they were made in China and loaded on a ship destined to Japan or they were modeled on Chinese mirrors and produced in Japan.
一方で、三角縁神獣鏡と同じようなものは中国では出土しておらず、中国で既に改元された年号や実在しない年号の銘が入ったものもあることから、日本製、あるいは中国から渡来した工人の製であるとする説、また、中国製で船で日本に運ばれた舶載鏡とする説、日本で中国の鏡を真似てつくった倣製鏡説などがある。