The listing, 1976 National Bicentennial Medal (Coin) has ended.
Any commemorative coin has to be approved and ordered by congressional act. Most were to raise money, but it seems like the bicentennial was a time to go commemorative crazy. Some of our regular coins had their reverse replaced with patriotic symbols. These designs were the subject of a contest, with the winners remaking our quarter, half, and one dollar coins.
This National Bicentennial Medal was also made by the US mint to raise money for scholarships,and were minted using different metals. Since this was also an Olympic year, they were made in Gold, Silver, and Bronze. However, the Bronze ones were made in a regular version and a gold-plated version.
I can tell by weight that this isn't gold, and it's clearly not silver. It's about the size of a 50¢ piece, so the weight comparison was easy.
Thus, it's one of the bronze ones, but I can't tell which. It was encapsulated at the mint, and is impossible to open. And a gold plated one would weigh almost the same as a pure bronze one. So, there's an element of chance here.
Thirty-eight years ago, in 1976, the bronze medals were $5.00, the gold-plated bronze were $15.
Details on sizes, weights, cost, number minted, etc. can be found in the original Congressional report, page 28:
http://www.bookprep.com/read/mdp.39015027058018
Bids start at 1976.