Auctioneer David Kleiweg de Zwaan intonated, gesticulated, congratulated as he nudged up the price of a Chinese 18th-century “large and magnificent imperial” zitan mirror stand from its US$50,000 starting price. “I’m selling, last chance,” he called at Christie’s auction house in Rockefeller Centre, dressed in a blue suit and grey tie, surveying an in-person, internet and phone bank crowd of collectors