Get the Popular Science daily newsletter💡 Breakthroughs, discoveries, and DIY tips sent six days a week. A metal detector hobbyist discovered a centuries’ old coin while scouring an abandoned sports field—and the coin  is especially rare for the area. In the southern Australian province of Victoria, treasure hunting enthusiast Angus James recently spotted a well-preserved 100 Mon Tenpō Tsūhō, a 19th century Japanese coin likely deposited during Australia’s decades’ long gold rush. “You never know what you’ll find next,” James posted to social media on January 25th, along with photos of his recent haul. Australia’s gold rushes began in 1851, and quickly became transformative events in its history. Although already home to many diverse Indigenous groups, the United Kingdom had overseen penal colonies on the continent for nearly 100 years prior to the precious metal’s discovery. However, once word of the gold spread, people from around the world raced over to stake their own fortunes. By 1871, Australia’s total population had risen from around 430,000 to over 1.7 million inhabitants. The coins are both collected …