Christie’s is previewing its Classic Week auctions, with Fabergé’s Imperial Winter Egg expected to sell for more than 20 million pounds. Commissioned in 1913 by Tsar Nicholas II, the rock-crystal egg has twice set world records at past Christie’s sales.  Margo Oganesian says it holds “4,508 diamonds, believe it or not,” calling it an “absolutely stunning creation” that was exceptionally difficult to make.  Dutch painter Gerrit Dou’s early work “The Flute Player” also leads the Dec. 2 auction with an estimate of 2 million to 3 million pounds.