This excerpt taken from the DPL DEF 14A filed Mar 17, 2006.
Option Rights. Option rights may be granted that entitle the optionee to purchase common shares at a price not less than market value per share, determined as the closing sales price of the common shares as reported on the New York Stock Exchange Composite Tape on the day immediately preceding the date of grant. These may be either non-qualified stock option or incentive stock options (ISOs). No option right may be exercisable more than 10 years from the date of grant. Each grant will specify the vesting schedule of the option, provided that, except in limited circumstances, option rights may not vest by the passage of time sooner than one-third per year over three years or one year from the date of grant if subject to the achievement of Management Objectives (described below).