On September 1, 1923, the Great Kanto Earthquake struck the Kanto plain, triggering widespread fires that consumed Tokyo. At the Japanese Bureau of Engraving and Printing, officials believed their most precious assets—the hand-engraved master printing plates for paper currency—were safe inside a newly built, fireproof underground vault. However, the sheer intensity of the firestorm transformed the subterranean chamber into a giant kiln.
Superheated air trapped inside reached extreme temperatures, liquifying metal and destroying the intricate steel and copper master plates used to print banknotes. With the printing infrastructure destroyed and paper currency literally going up in flames across the city, the Japanese government faced an unprecedented economic crisis: a severe shortage of physical cash amidst a massive humanitarian emergency. To prevent financial collapse, emergency bills had to be hastily designed and printed on simplified plates, leading to temporary emergency-issue notes that lacked standard anti-counterfeiting watermarks and fine details.
The disaster reshaped currency design and vault engineering standards in Japan for decades to come.