Did this machine spend some time in a bar? It's probably nicotine residue. It's a yellowish residue that will harden over time. You will have to remove the translite. Clean the glass and translite thoroughly. The cabinet is probably coated as well. You may not notice it due to the black colors. I once had an EM game that was coated with the stuff. I cleaned it outdoors with a TSP solution, it looked amazing when I was done. TSP would be fine for your glass but is probably too harsh for your translite.