This is a No No. Do not try to clean or restore this Baseball. You will most likely do more harm to it. Restoration to any collectible should be left to the expert that has experience with that type of work, and to this day I have never heard of anyone that restores baseballs or signatures. Sharpie is not used for signing baseballs because of the porous properties of the baseball will absorb the ink and it will tend to bleed. The same thing will happen if you try to clean it. The stain might lighten, but will spread to a larger area of the ball. What ever you use to remove the stain (or yellowing) will have no problem removing the signatures as well. If any liquid comes in contact with the signatures, your baseball will look like a wet piece of mail.
Bobby Brown American League baseballs made around 1984-1990 that have "Haiti" placed under the Rawlings logo stamp were made without the use of distilled water. This allows for enzymes to potentially turn the color of the ball over time. It will cause yellow/brown soiling on these baseballs due to the flaw in production. It might not happen to all baseballs but your baseball might be one. The Ideal conditions for display would be indirect lighting, at a room temperature of 65 - 70 degrees, and 50% humidity. Always check your signatures periodically for signs of fading or deterioration, and avoid excessive handling.
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