Quoted from paulears:
........I just wish I knew how it got this black inside - in the picture you can see the state of the label - pretty grim.
Thanks for the welcome - appreciated.
Have come across this level of grime before. From your picture it looks like its never had a clean since it left the manufacturer. Also looks like the switches have been 'lubed' liberally at some time probably with a spray (Maybe WD40 or such) that has eventually become a contact glue.
I buy games that i will keep not sell on, so this game condition is fine for me as I totally strip down and clean every surface and remake labels etc. If you are going to sell on in a year or so then ...oh dear you need to take out the bottom board and give it the Aussie treatment with some degreaser and a hose. Save the labels first and remake them. Won't hurt it.