This excerpt taken from the SYT 20-F filed Mar 16, 2005.
Syngenta Treasury Shares (Unaudited)
Since the formation of the company, Syngenta has held treasury shares purchased as part of the merger agreement. On February 11, 2004, Syngenta sold 4.5 million of these treasury shares and at the same time bought an equity instrument over the same number of Syngenta shares. The equity instrument was still outstanding at December 31, 2004, as disclosed in Note 23. Subsequently, Syngenta sold this equity instrument and acquired 4.5 million of its own ordinary shares on the second trading line. These shares will be proposed for cancellation at the 2005 Annual General Meeting (AGM) of the shareholders. A second trading line is how share repurchase programs are commonly operated in the Swiss market. It enables the seller of the shares to reclaim withholding taxes on the shares sold for cancellation.