I just acquired this game and am puzzled by the knob on the lower right apron. It is connected to nothing below and I'm wondering what I am missing in the game. I could use a picture of the underside to see what should be there. Thanks.

That makes perfect sense now. I could feel the metal piece in the center flex when I lifted it and that playfield does seem unusually heavy. It's just missing the washer and clip. Thank you!