WordPress 1.5.1.2 was released May 27, 2005.
The official release can be found here.
List of Files Revised in 1.5.1.2
/wp-content/themes/default/header.php
/wp-includes/functions.php
/wp-includes/template-functions-category.php
/wp-includes/template-functions-general.php
/wp-includes/version.php