The FT.com goes into the details of the calculations of eligibility for the Standard Life floatation windfalls:
…anyone who took out a with-profits policy before March 31 2004 – will receive a fixed payout of 185 shares to compensate them for loss of membership. On top of this, virtually every member will receive an additional number of shares, based on how long they have held their with-profits investments and how much they are worth.
More articles on the Standard Life demutualisation: