It's the most non-reactive metal, meaning it doesn't corrode or oxidize. It reflects all infrared energy, making it about the best radiation shield (great for coating spacesuit visors). It has extremely high electrical and thermal conductivity in a wide temperature range. It's the most ductile metal known, meaning you can make extremely thin wires or sheets that still hold together. And by thin, I mean an ounce of gold can make a five mile-long wire.
In all, I'd say it's pretty valuable.
Bingo. Not to mention that these coins are EXTREMLY rare whether acquired legally or not.