I haven't restored or clear coated mine yet. I did touch up the black outline around the window with a black paint pen and followed up with a brush on coat of clear varnish.
While not a permanent solution, it will protect the area while being played.
To prevent further wear, its advised to level the window with new rubber washers.
Black hole was a lot easier to do than my haunted house. The diamond pattern around the window was tough to color match. Eventually they will both get restored and clear coated.