This paper explores the market for indeterminate works of art. Our data set includes 1578 sales of fifteenth and sixteenth-century anonymous Flemish paintings, mainly collected from the Blouin Art Sales Index over the period 1955-2015. After a brief introductory section to the issue of anonymity in early modern art, and the different situations of information failure generated by anonymous paintings, the empirical part examines the supply and demand for paintings by unrecorded artists, using a hedonic pricing model. We find evidence that the degree of specification of the spatio-temporal designations given to the paintings (e.g. Flemish school, sixteenth century) affect prices differently (H1). The more specific the designation is in time and space, the more it tends to make up for the lack of information, and to positively affect the market value of anonymous paintings. When the artist name is missing, we also argue that purchasers pay greater attention to other quality signals. Four other hypotheses, which are expected to influence the buyer's willingness to pay, are successively tested: H2) the physical condition of the painting; H3) oral or written interventions by an expert; H4) the length of the lot essay; and H5) previous attributions to named artists. The results suggest that most of these variables operate as significant pricing characteristics. We finally compare price indices of named artists, indirect names and spatio-temporal designations.