In countries with poor identification document utilization or standardization, electoral ink (aka indelible ink) is used to prevent voter fraud. The silver nitrate in the ink can stain the skin for up to a couple weeks. – WTF Fun Facts
Source: https://en.wikipedia.org/wiki/Election_ink
WTF Fun Fact – Election Ink
Since the US can’t agree on photo ID for voters, why not use the third world method ?? Whattaya say, Schumer ?? Fair enough ?