When William Knox D’Arcy signed the first oil concession agreement in the Middle East with the Iranian government in 1901, he encountered numerous problems. This was due in part to the costliness of the venture and his failure to strike commercially producible quantities of oil in the first seven years of the concession’s existence. The problem was that the 1901 oil concession did not say much about the oil or where to find it. One of the first socio-technical problems British investors had to solve was how to attach property rights to a subsoil material owned by a foreign government in a region where local forms of property ownership already existed. No existing history of Iran, or of any other country in the Middle East, deals closely with the development of oil by taking seriously its technical and concessionary history. Based on archival research in Iran and the UK, this paper places technologies of accessing, measuring, valuating, and selling oil at the center of the analysis in order to trace the political construction of British concessionary property and its role in shaping alternative political possibilities in the control and distribution of oil. British investors, managers, and engineers arrived to southwest Iran with a peculiar understanding of the properties of oil – the terms and politics through which they would access and exploit oil as spelled out in the concession’s text. They also confronted what they viewed as a desolate backwater inhabited by a population lacking the adequate technical knowledge and skills for modern energy development, yet possessing claims to ownership of the regions targeted for oil extraction. Placed by the company in apparent opposition to the history of democracy and modernity of the West, these local actors created a kind of uncertainty most evident in the problems that emerged around the question of British concessionary control over the oil. The paper starts from the concession agreement itself, treating the articles on property not just as a text over which the main actors disagreed, but as an apparatus through which actors take on new powers and politics. I argue that there were many rules of concessionary property, which conflicted with the building of international monopoly arrangements among the largest oil companies. The concession was highly uncertain because its articles maintained a flexibility and ambiguity that could be exploited by multiple sides, helping to constitute the political agency of the multinational oil company.