I can confirm for you that the Columbia Mint sold miniatures of the $50 Panama-Pacific octagonal gold coin back in 1980. Your piece is a medal not a coin. Your medal appears to match the images of the Columbia Mint medal, but I can't be 100% sure.
The piece was marketed back in 1980. Early in the year it was struck on a 22K planchet (i.e., 0.900 fine gold), but from September on it was advertised as being of 24K gold (i.e., pure gold). Regardless, the medal was always sold for $50 plus $2.00 postage.
At 0.5 grams, the piece has about $23.50 worth of gold (as of 11/18/2019). Its value is tied to its intrinsic value as it does not have much demand among collectors.