It is a commemorative coin issued to celebrate what is written on the coin - the discovery of America.
They made over a million of them for the Exposition in Chicago in 1892-93. It was fairly common for them to circulate at the face value of $0.50 after that, explaining why many of them are circulated. That example is probably worth $7-10.
The Columbian Expo opened on Columbus Day, 1892. It was only open for a short time, and then re-opened in 1893. That is why the conis were issued for two years. By the way, there was also an Isabella quarter commemorative issued, honoring the Board of Lady Managers, for this expo. The quarter was a much lower mintage and is worth far more.
i think they are neat looking, but common. i've actually heard a few people found these in boxes and rolls of halves!
