In all fairness, they probably aren't worth the cost in your time and any chemicals ( even distilled water ) you may use. If you are going to sell for silver value, leave the dirt on. If you really want to keep them as your first, and you recognize the difference between "dug" coins and collectors coins of value, then realistically use a soft tooth brush and detergent water and gently take off the dirt and then rinse well with tap water and dry. I think dug coins whether modern or ancient falls under different rules for cleaning than others. There aren't many worse things you can do to a coin than bury it for several decades or centuries. IMO. Jim
