I think you will find that despite its gold like appearance that the coin is actually "silver". I found information on a 1987 Englehard American Prospector Pure Silver Round .999 silver 1 troy oz. at the sites listed below.

Also, several similar coins though with different dates can also be found on ebay. The prices seem to range from starting bids of $12.50 to about $29.95.

Another site (rivertinkers.com) are selling the 1984 & 1985 coins of the same description (called "Rounds") for $35.00. The site also states that generic rounds are selling for slightly less at $30.00 a coin.

I found a great PDF file on your coin which I have also listed below.

I did read this and found it interesting: " ... because of the 1986 release of the American Silver Eagle --- Englehard ceased production of the Prospector after 1987. "

I hope this information has been useful to you.