In England 800 years ago, an ounce of gold was worth about 6 months unskilled labor.[1][2] Today, it's worth about 3.5 weeks.
In the past century, gold has underperformed U.S. equities and has not, in any case, held its value very well. It's been quite volatile, e.g. falling 30% in 2013.
The article doesn't say how much gold this coin contains, but its value is essentially 100% numismatic.