The Railway Express Agency has not existed for a long time. I do not know what the sign is made of, but have been told that it's probably masonite. I do not think that it's tin, but rather some kind of plastic.
Also, the sign is enclosed in a wood frame. The size is 45 1/4" x 45 1/4". The item "Large Antique Vintage Collectible Cola Display Sign. Very Rare Advertisement" is in sale since Tuesday, April 24, 2018.This item is in the category "Collectibles\Advertising\Soda\Coca-Cola\Signs". The seller is "amchoul" and is located in North Attleboro, Massachusetts. This item can be shipped to United States.