It's the "eye" that sees when a coin is ejected through the outlet slot.
So the the thing that hangs out of the hopper and where the coin comes out?
I'm no expert, and I've never seen the inside of a machine properly as I've never actually owned one, but is it normal for it to be full of cobwebs? I know spiders get in anywhere, but as far as I can remember from when I used to play and they opened them, cobwebs were not the 'norm'?
It's kept in my shed and there's a fair few spiders around.