Someone stole a really big gold coin
The idea for the Big Maple Leaf coin formed as the RCM was launching a new series of pocket-sized coins made of 99.999 percent pure gold, often referred to as “five nines pure.” Raw gold is typically muddied with other elements like silver, aluminum, or zirconium, and needs to be processed so that there are less than ten parts per million of other elements. The typical standard is four nines. That extra decimal represents hundreds of thousands of dollars of additional value, and a source of technical pride for an organization like the RCM.But the RCM wanted to signal a little more to the world, to draw attention to the new line of coins. In 2004, the Austrian Mint had created what was at that time the world’s biggest coin: a 31 kg coin made of 99.99 percent pure gold. In doing so, Austria hadn’t issued a direct challenge, but because there is an unofficial rivalry between international mints, they might just as well have. What if the RCM combined one accomplishment with another? What if they created a big, 99.999 percent pure coin? Really big. Big enough to draw attention.
Read the whole thing, it's fascinating.