pardon the delay. after one app of Lysol letting it soak & some more scrubbing with the pumice stone here is where I'm at. (cant get a pic to load but will keep after it). EDIT got it!
Put some Sno-bol or similar product in there and let it soak for many hours or a day or two... Keep going back periodically with a toilet brush to remove it as it loosens and breaks down the grime...