An interesting valuation case has just been concluded: Coleridge v Sotheby's  EWHC 370 (Ch).
It concerns the Coleridge Collar. That is a gold chain of office that was worn by the judge Lord Coleridge while he was Chief Justice of Common Pleas until 1880, when the post was abolished. Historically, the chain had been passed from officeholder to officeholder for a nominal sum and so was always owned by the holder. With no one to pass it on to, Lord Coleridge kept it. It remained in the family, until it passed to the current Lord Coleridge. In November 2006, he sold it privately for £35,000, on the basis of a valuation from Sotheby's of £25,000-35,000. Two years later, the purchasers sold the collar at auction at Christie's for £260,000. (report)
The main area of difference between the opinion of the appraiser at Sotheby's and the catalogue preparer at Christie's was about the age of the collar. Sotheby's concluded that it was made in the late seventeenth century, whereas Christie's believed that it dated from the mid-sixteenth century. Inevitably, Lord Coleridge argued that Christie's were right, but on balance the judge sided with Sotheby's on the point. Even so, Sotheby's valuation looked remarkably low.