What is the value of a 1492 Columbian half dollar?

Uh, please take another look at both the coin and a history book. The coin has the Words "United States of America" and "Chicago" on it. The US didn't exist until 1776, the first half dollars were made in 1794, and Chicago was named in 1833 so how could it be from 1492?

If you look more at the back of the coin, the minting date 1892 or 1893 will be prominently show below the two globes. There's more information at the Related Questions.