US bills use both, and the invisible watermarks have proven their value. Imperceptible imperfections intentionally (yay, illiteration) placed on 100 dollar bills have managed to catch advanced North Korean forgery attempts. Same goes for magnetic inks and all kinds of visible and invisible watermarks on US currency.
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US bills use both, and the invisible watermarks have proven their value. Imperceptible imperfections intentionally (yay, illiteration) placed on 100 dollar bills have managed to catch advanced North Korean forgery attempts. Same goes for magnetic inks and all kinds of visible and invisible watermarks on US currency.