Treffer: sented every year and a set of accounts was finally approved by the Board of Directors in October 1832. From these accounts came a steady stream of information in the form of reports from the chief accountant to the Board of Directors, including sets of unitary costs at every stage of the manufacturing process. Moreover, the directors frequently visited the branches of the Company.7 Those three elements combined to create a real Decision Support System. The Manufacturing Process. Before going into the accounting problems, it is worthwhile to describe briefly the operating process for glass. Glass production can best be described as follows: from several raw materials (silica, soda and lime) they produced glass by pouring and flattening it in order to give it its plane shape; the glass was then annealed in order to improve its mechanical qualities. After that 'hot process', the 'cold process' began, to rectify or get rid of the shortcomings of the flattening; it was divided into two stages: abrasion, called 'douci', gave the two faces their parallelism and general flatness; then polishing, called 'poli', to improve the quality of the surface; after abra­ sion, the sheet of glass was translucent but not transpar­ ent, because it was still slightly grained, and it only turned perfectly transparent at the end of the polishing [Daviet, 1988]. In accounting for the production of glass, the company made a distinction between the costs of pouring, abrasion and polishing. Charges were not classified according to their nature, but to their place in the manufacturing process. During the 18th Century, the Company had four branches: its Headquarters in Paris, a mirror factory in Saint-Gobain (Aisne), another in Chauny (Aisne), and a soda factory in Chauny. The first document available is a Profit and Loss Account (Compte de revient) dated from June 30, 1826.8 This Profit and Loss Account was organized according to the in­ ventory production and corresponds to the period beginning July 1, 1825 and ending June 30, 1826. Details of this account are shown in Table 1