LONDON.- A magnificent and important pair of porcelain vases by the Imperial Porcelain Factory will highlight this autumn’s Russian Art Week in London (estimate: £1,700,000-2,200,000). In their 28 November Russian Art Sale, Christie’s will offer perhaps the finest and grandest pair of Russian porcelain vases to appear at auction in recent memory. Over the years, Christie’s have been entrusted with the sale of numerous important pairs of Russian vases and have achieved the highest price ever paid at auction for a pair of Russian porcelain vases in 2006. These magnificent vases were presented by Emperor Nicholas I to Karl Ludwig Graf von Ficquelmont (1777-1857), who served as the Austrian Ambassador Extraordinaire to the Russian court from 1829-1839. Graf von Ficquelmont was