Good thing you are a digger,my friend!
It looks to be a neck hanger, probably had a chain attached at the loops. There were watch fobs, suspender clips, commemorative coins made from aluminium, the new "Miracle Metal" among other things. The US government issued stamps along with a commemorative half doallr, too.
The 19th century was an age of expansion and invention unrivaled in America and the 1893 World's Fair in Chicago was a celebration of our involvement in that. Here's a tidbit:
"The World's Columbian Exposition, held in Chicago in 1893, was the last and the greatest of the nineteenth century's World's Fairs. Nominally a celebration of Columbus' voyages 400 years prior, the Exposition was in actuality a reflection and celebration of American culture and society--for fun, edification, and profit--and a blueprint for life in modern and postmodern America."
Here's a great link to tell you about it:
http://xroads.virginia.edu/~MA96/WCE/title.html
The Trash Man,