唐代發行貨幣，鑄量較大的有三種，一是開元通寶，一是乾元重寶，另一種則是背字的開元通寶型態，俗稱會昌開元，因為鑄於武宗會昌年問(841-846)之故。會昌開元的背字，至今已發現二十三種，分別是昌、京、洛、荊、襄、鄂、潭、益、梓、興、潤、宣、丹、廣、桂、福、永、平、藍、兗、越、梁、洪，形成一種特殊的鑄造型式，後世認為這是中國貨幣背紀鑄局的濫觴，也是晚唐、五代主要使用的貨幣。 既然如此，錢背背字應當是具有地域意義的，然而會昌錢仍舊與後世清代各省鑄造貨幣錢背省局，有很大的不同。以清代為例，各省局鑄幣必須遵從中央的貨幣政策，這可由年號錢的含銅量、字形版式線索中可以看出。但會昌開元二十三種背字，雖多是地方行政單位，但版式紛亂，鑄量大，這裡面隱含了幾個問題，一、為何錢須背字？二、錢背字有何地理上的意義？三、錢背字有何政治或經濟上的意義？四、為何是這二十三種背字？五、為何沒有與傳統學界關注的割據藩鎮－河北諸鎮，有相關地名的背字？本文意圖在這些問題中，尋求除了多年以來學界著重從稅法、專賣事業、地理形勢等議題的角度，了解中晚唐經濟地方問題的真相外，另外以貨幣發行區域為切入點做分析，來反映出當時帝國內部經濟網絡變化的情形。

There were three major currency of Tang Dynasty: Kai-yuan-tung-pao, Chien-yuan-tung-pao, and Kai-yuan-tung-pao with carved words on backs which was nick-named "Hui-chang Kai-yuan" for it was published dury the period of Tang Wu Emperor's Hui-chang years (841-846). Since then, there are twenty three kinds of words carved on Hui-chang currency, forming a special layout of copper-money. It was the main currency in Tang and Wu-dai period. Later on, people take it as the beginning of "The China Currency Bureau". Nevertheless, back-carved currency should have area-meanings, very different from those of Ching Dynasty. Currency Back-carved Bureau in Ching had to obey the government's currency policy. We can find out many proofs in yearly currency, e.g. the copper content, the types of carved words etc.. However, the Hui-chang 23 kinds of back-carved were not proposed by local administration, and the layouts were so much different. Therefore, there are many questions: 1. Why the currency should be back-carved? 2. Is there any geographical meaning among the back-carved currency? 3. Any economic meaning? 4. Why the particular 23 kinds of back-carved? 5. Why there are no back-carved related to the regional occupied power that was always in consideration of traditional research? This article tries to find out the economics problems from the middle till the late Tang's period by a new ankle in addition to tax, monopolize, geography.