WordPress at a glance
function is not described

post_thumbnail_meta_box() WP 2.9.0

Display post thumbnail meta box.

No Hooks.

Return

Nothing (null).

Usage

post_thumbnail_meta_box( $post );
$post(WP_Post) (required)
A post object.

Code of post thumbnail meta box: wp-admin/includes/meta-boxes.php VER 5.1.1

<?php
function post_thumbnail_meta_box( $post ) {
	$thumbnail_id = get_post_meta( $post->ID, '_thumbnail_id', true );
	echo _wp_post_thumbnail_html( $thumbnail_id, $post->ID );
}