Filter WordPress Admin Body Classes and Append Post ID

filter-admin-body-classes-post-id.php

<?php

add_filter( 'admin_body_class', 'dbr_mod_admin_body_class' );

/**
 * Append Post ID to Admin Body Classes 
 */
function dbr_mod_admin_body_class( $classes ) {
    global $post;

    if ( is_object( $post ) && is_a( $post, 'WP_Post' ) && property_exists( $post, 'ID' ) ) {
        $classes = $classes . " wp-post-" . $post->ID;
    }

    return $classes;
}