I am in the process of reviewing my TZ to upgrade the lighting, and noticed there is a hole cut into the play-field near the piano (see photo). Can someone please advise what the purpose of this hole is for (drilled for a mod, or possibly something was removed from the original machine)? I also looked in the manual and cannot determine what it is for. I have only owned the game a few months so I am still learning as I go. Thanks in advance.