STUTTGART, Germany, a cold Wednesday last week. Not far from the city station, a big tent has been converted into an ultramodern auction hall. The auctioneer is doing brisk business, quoting lot numbers, shouting out prices and accepting bids. To his right and left, two huge screens display catalogs with details of the ancient ceramics on offer.

An audience of about a hundred was there. They came from around the globe—Germany itself, Brita