The concertos for one harpsichord, BWV 1052–1059, survive in an autograph score, now held in the Berlin State Library. Based on the paper's watermarks and the handwriting, it has been attributed to 1738 or 1739. As Peter Williams records, these concertos are almost all considered to be arrangements by Bach of previously existing works. Establishing the history or purpose of any of the harpsichord concertos, however, is not a straightforward task. At present attempts to reconstruct the compositional history can only be at the level of plausible suggestions or conjectures, mainly because very little of Bach's instrumental music has survived and, even when it has, sources are patchy. In particular this makes it hard not only to determine the place, time and purpose of the original compositions but even to determine the original key and intended instrument.