Imjinja is a metal type made during the reign of King Yeongjo (r. 1724-1776) in the late Joseon Dynasty. Korean metal types date back to the Goryeo Dynasty, and the tradition flourished in the Joseon Dynasty, where there were more than 30 known projects for casting and improving official sets of type. Imjinja type, which includes 150,000 newly cast types, was based on gabinja type, which was used for the Heart Sutra (心經) and Curative Measures for All Diseases (萬病回春). The imjinja types were kept in the royal printing office, Gyoseogwan (校書館), and they were one of two official types, along with jeongyuja, which was made in 1777 (first year of King Jeongjo). A fire destroyed the jeongyuja type in 1857 (eighth year of King Cheoljong), so only imjinja type was used thereafter.