Demosthenes (382-322 BC) wrote numerous legal speeches, which provide a plethora of cues about public and private law in Athens during the 4th century BC. In his speech “Paragraphe pros Pantaineton”, Demosthenes described a complex financial transaction composed of a sale, a lease, and a loan. The speech further documents the conditions, under which a mining entrepreneur obtained credit to finance a factory among the silver mines of Laureion, near Athens. In this article, I first review the available literature concerning this speech since the 19th century. The historical analyses have so far focused predominantly on the institution of "prasis epi lysei", which is not referred to in any ancient legal speech, and have not been conclusive about the nature and operation of this ancient contract. As a consequence, this transaction has remained obscure for centuries. With the present article, I attempt to decode this mysterious transaction. I start from the premise that it is widely acknowledged that Demosthenes was one of the most experienced lawyers of his time. Thus, I take his speech at face value and examine it as a legal brief featuring the essential elements (essentialia negotii) of the disputed contract. In the absence of ancient Athenian legal archives and codices from the 4th century BC, legal speeches are, in principle, the only available documents reflecting the legal and contractual provisions applicable at the time. Consequently, I examine the contract from a purely legal perspective using contextual interpretation in combination with the comparative legal method. Finally, I compare the ancient transaction with contemporary finance leasing, which is a synthetic contract composed of a sale, a lease and a loan. My legal analysis provides insight into a fascinating world of diverse property and contractual rights, which were combined in ingenious ways to secure the financing of the industrial production of silver over the ages. These rights were documented by means of written deeds and enforced by courts in case of disputes or market stress. The Laureion silver, which was used to mint coins, or to finance grains imports from the Black Sea region, was essential for the monetary system and the economy of ancient Athens. Sophisticated contracts helped build a strong Athenian economy and could become a source of inspiration for contemporary economies. I conclude that further legal analysis of ancient speeches may help us better understand the significant contribution of ancient contract and property laws to the development of economy and democracy in ancient Athens
