Any Information on this large 6" diameter medallion would be greatly appreciated

Interior appears to be copper, with boarder an undetermined silver colored metal

Blank reverse is hand marked E106A / Hale 239 with black sharpie.

 Quote: This item is a bronze relief medal commemorating the 400th anniversary of Christopher Columbus's voyage, specifically designed for the 1893 World's Columbian Exposition. 
Designer/Sculptor: Designed by Lodovico Pogliaghi and sculpted by Angelo Cappuccio. 
Depiction: The scene shows allegorical figures representing "Civilization" holding 

a cornucopia above American Indians. 
Details: It is highly detailed and often found in a bronze or copper electrotype finish. 

 The silver-coloured border was added later. 

 https://www.invaluable.com/auction-lot/1893-worlds-columbian-exposition-columbus-portrai-4201-c-1084ca893d 

 It was Lot# 71 in a 2006 auction - 

http://www.worldsfairauction.com/catalogs/catalog-4.pdf 

 Quote: Bronze Medal, Eglit # 105, pictured on the cover of Eglit "Columbiana" book.
This medal pictures bust of Columbus on the Obverse with inscription: "Christopher
Columbus", in outer band "Memento of the World's Fair Chicago 1893" in small letters
"Johnson". On the reverse: in the center the figure of "Civilization" surrounded by Genii.
Below an Indian warrior. To the left, the Capitol (and this is really small) and around the
edge are the coats of arms of the states. Size: 2 1/4 inch diameter by 1/8 inch thick. 

 So maybe the E106A is Eglit # 106a catalogue number, 

with yours being a larger size, and Hale 239 is a different catalogue. 

 Here are the two small details mentioned above … 

Thank you  for the information. Any idea as to the value? Rich