익산 평장리 유적에서는 한반도 서남부에서 유일하며, 한반도 남부에서 가장 이른 시기의 중국 거울인 四葉四螭文鏡이 출토되었다. 이 동경은 岡村秀典과 김일규 등이 위만조선의 동경으로 인지하였으며, 중국 淮河 유역에서 기원전 2세기 중엽에 만들어져 한반도 남부로 유입된 것으로 이야기 되고 있다. 최근 중국 전국-진한의 동경 연구성과를 바탕으로 익산 평장리에서 출토된 사엽사리문경을 살펴보면, 제작 시기는 전국시대 秦이 楚를 병합할 즈음인 기원전 3세기 말까지 거슬러 올라갈 가능성이 높으며, 익산으로 유입된 시기는 준왕이 남하하고 위만조선이 성립한 기원전 194년 이전일 가능성이 있다. 그렇다면 이 동경을 중국 중원에서 한반도 남부까지 옮긴 주체는 마한과 준왕이 이끈 고조선으로 볼 수 있다. 중국-고조선을 잇는 교역로는 철기를 운반한 육로와 유리, 중원식동검을 운반한 해로로 연결되며, 육로는 河北省 易縣 燕下都를 중심으로 한 전국 燕과 이어지며, 해로는 山東省의 齊, 그 남쪽의 楚와 연결되는 것이다. 또한 고조선-마한을 연결하는 것은 해로이며, 준왕이 남하하고 위만조선이 성립하면서 한반도 남부와의 교섭은 마한이 아닌 진한으로 주도권이 넘어가게 된다.
The Chinese bronze mirror was excavated from the site of Pyeongjang-ri, Iksan, in the southern part of the Korean Peninsula. It was proved to be the earliest of the bronze mirrors produced in China and excavated in the Korean Peninsula, and nowhere else in southwest Korea had Chinese bronze mirrors ever been discovered for quite a long time until the Later Han. This bronze mirror was identified as the artifact of the Wiman Joseon Dynasty by Okamura Hideji and Kim Il-gyu, both of whom agreed on the view that it had been produced in the basin of Huaihe, China, around the middle of the second century BCE, taking the west sea, or the yellow sea, route into the Jeonbuk province, part of Mahan, Korea. The recent research on bronze mirrors of Qin-Han dynasties could confirm the view that its production is likely to date back to the late 3rd century BCE on the grounds that the dragon motif and the repeatedly stamped fine-line patterns on the back of the mirror are known to have been popular during the late Warring States Period and during the early Han Dynasty, respectively. Prestige goods imported from China to Korea in those days travelled either overland or by sea. The land route was connected to Yan, one of the Warring States, primarily carrying iron products, and by the sea route circling around the Yellow Sea through Gojoseon to Mahan (the ‘Transellow Sea Trade Route’) were carried glass products and Chinese-style bronze swords. This sea trade route was also extended southwards to Qi and to Chu in the mainland China, and the supply and demand of bronze raw materials in particular took place along this trade route. Thus it is reasonable to assume that the bronze mirror in question was traded along this Trans-Yellow Sea Trade Route. Subsequently, it may have been introduced through Gojoseon to Iksan, Jeonbuk, before 194 BCE, when Junwang, perhaps along with the bronze mirror, was forced to move south into Mahan territory by Wiman, who established Wiman Joseon and exercised control over transport of goods between China and Korea. Probably for sociopolitical reasons, this resulted in Mahan’s losing trade connections with China through Gojoseon and, in turn, Jinhan, not Mahan, taking the leadership of the South in the economic context. It is very unlikely, therefore, that artifacts like this bronze mirror could have reached Mahan territory, presumably after the founding of Wiman Joseon.