Fill a small bowl or cup with enough lemon juice to submerge the coin.
Submerge the silver dollar in the lemon juice.
Allow the coin to soak for six to 24 hours. The more mildew present, or the thicker the layer of mildew, the longer the coin should soak. Do not allow the coin to soak for longer than 24 hours. Remove the coin.
Brush any remaining mildew from the silver dollar.
Rinse the coin in water to remove the lemon juice. Dry with a lint-free microfiber cloth.
Dampen a cleaning eraser.
Rub the eraser over the mildew. Continue rubbing, rinsing and dampening until the mildew is removed.
Rinse the coin under running water to remove any residue. Dry the silver dollar with a lint-free microfiber cloth.
Pour 1/4 cup of vinegar in a microwavable bowl or cup. Place in the microwave for 30 seconds, or until the vinegar is warm.
Dip a tissue into the warm vinegar. Wipe the tissue onto the mildew on the silver dollar. Continue cleaning until the mildew is removed.
Rinse the silver dollar under running water to remove all vinegar residue. Dry the coin with a lint-free microfiber cloth.