OK......my SE has those holes also but they are not for the mounting of the panel........I really didn't pay too much attention but will look closer tomorrow......right now they are I guess just covered with the panel. It is secured from the top..........
Edit...........guess I should have read page 2...............The 6 holes make sense now...........but mine was secured from the top............Factory...........
Don't know........Built in Oct of 69..