The quick and simple way to prevent fraud by detecting counterfeit currency. Ink works to react with the starch in wood-based counterfeit paper to leave a dark mark and expose false currency. Just mark a small line on bill and observe results: Amber indicates a genuine bill, while black/dark brown means bill is suspect. Features naturally-occurring, long-lasting antimicrobial technology, which protects against the growth of bacteria on the surface of the pen. For best results, replace cap immediately after use.