Try boiling in destilled water plus detergent (and/or soda). This may solve the oils and uncover/brighten sand and
patina residues.
By this method you may get more contrast on the coin by increasing the rough areas and reducing the polished shining surface.
Some tricky guys glue dust or sand in deeper areas of their overcleaned, shiny ruins and create artificial sand patinas hiding corrosion and defects - but that´s a far out method often used by crooks.
But if you manage to attach a
fine dust to improve the contrast and general appearance, increasing details and hiding nothing, just for your own pleasure - why not.
