Dividends on A Shares will be paid, by default, in euro at the rate of €0.3421 per A Share. Holders of A Shares who have validly submitted pounds sterling currency elections by August 24, 2012 will be entitled to a dividend of 27.08p per A Share.
Dividends on B Shares will be paid, by default, in pounds sterling at the rate of 27.08p per B Share. Holders of B Shares who have validly submitted euro currency elections by August 24, 2012 will be entitled to a dividend of €0.3421 per B Share.
This dividend will be payable on September 20, 2012 to those members whose names were on the Register of Members on August 10, 2012.
Source:
http://www.shell.com/media/news-and-media-releases/2012/q2-2012-pound-sterling-euro-announcement.html