The modification and the destruction of legal tender such as coins is not punishable. Please note that any modification compared to the original state (e.g. colouring, gold-plating, silver-plating, printing) renders the coin worthless as legal tender. All legal tender valid in Austria is published in the "Elektronische Verlautbarungs- und Informationsplattform des Bundes" with all specifications and their optical appearance.
Please contact your bank. It can submit the damaged coins for you.
Under no circumstances should counterfeit money be spent. If you have a suspicious coin, bring it to the bank. In accordance with the National Bank Act (Nationalbankgesetz), credit institutions are obliged to withhold counterfeit banknotes and coins. The bank will record your data for the possible reimbursement of the value and issue a receipt as confirmation. The suspicious banknote is then sent to the Austrian National Bank and coins to Münze Österreich AG for examination.