Especially since at the bottom of that part for the coin it lists the weight as 15 grams. That's not 1 oz of gold. To boot, gold is one of those things that doesn't really darken, it tends to stay the same color at any angle, and seeing shadows makes me think that this is in fact a zinc-plated coin, as you can get close to a gold tint with zinc electroplating on copper. That would be more reasonable given the weight, assuming all other dimensions are correct.