Use a safe cleaning technique, such as cleaning with water and a mild soap using a soft toothbrush. Preferably use distilled water to rinse. If the item is not clean after you've done this, try a soft brass brush. If the item is still not clean, try a mild acid solution for precious metals, and a stronger one if necessary. In both cases prepare a low concentration first and a high one afterwards, and keep the first cleaning session short and the second one a bit longer. Chemical cleaners may seriously harm the items.
Cleaning retrieved coins
Have you found a numismatic item? We can advise you on the best way to clean your find.