Some varieties from the reign Hong Wu (1368-98), mint at Fuzhou, Fujian Province. First coin with Fu below on reverse can be dated to 1368-69. Second coin later. Two varieties without mint character are from a period when calligraphy alone sufficed to identify mints.
Much of Fujian is physically cut off from the rest of China by mountains. It had its own dialect, Hokkien, and historically China's premier maritime trading ports. The 2nd through 4th pieces were exported to Japan, and copied there (among others) before a national cash coinage with Japanese inscription was established in 1626. The Chinese diaspora of the 1400's-1700's, to Indonesia, the Philippines, and the rest of SE Asia was also primarily of southern Fujianese people.