Part of the affect of the current enthusiasm for art in China is the national desire to bring back national art treasures spirited away during centuries past. An antique pair of silver door knockers is getting a lot of attention at a preview exhibition for the Rongbao Autumn Auction in Beijing. The door knockers were forged by the imperial architecture bureau, during the reign of Emperor Qianlong in the 18th century. They were made to be used in Yuanmingyuan Garden; the Old Summer Palace. It's a sprawling, garden complex located in Beijing's western suburbs. The compound was pillaged and destroyed by Anglo-Franco invaders during the 19th century. The antiques have just been returned to China. The door knockers were in the hands of overseas collectors for more than a century.