Congratulations! It looks like you have found a 1976 Olympic $100 Commemorative Gold Coin, when Montreal hosted the Olympics. Some details from one website include: "This Proof version of the $100 commem is minted in 22K gold, measures 27mm, weighs 16.97 grams and contains 1/2 ounce of fine gold. The coin is in mint condition and comes in the case of issue with outer box and COA."