The Khải Định Thông Bảo was a French Indochinese sapèque coin produced from 1921 until 1933, the design of the coin was round with a square hole that was used for stringing them together. Khải Định became Emperor of Annam in 1916 the funding for the production of new cash coins was reduced by the Hanoi Mint which lead to the demand of the Vietnamese market for low value denominations to not be met, furthermore, after Hanoi reduced funding for the Thanh Hóa Mint, which until that time was producing enough low denomination cast cash coins to meet the market's demands, which caused most, but not all, of the production of cash coins at the mint to cease in 1920. In response a new committee was formed in Hanoi which ordered the creation of machine-struck Khải Định Thông Bảo cash coins, these are the first machine-struck four character Thông Bảo (通寳) coins in Vietnam with the reigning emperor's name as the French government had prior tried to introduce a Cochinchinese 2 sapèque coin that continued under French Indochina that weighed 2.05 grams and had a nominal value of 1⁄500 piastre, later the colonial government of the French Protectorate of Tonkin had unsuccessfully tried to introduce a zinc milled sapèque produced by the Paris Mint with a nominal value of 1⁄600 piastre from 1905 until 1906. Unlike the earlier attempts at producing machine-struck cash coins by the colonial French authorities the Khải Định Thông Bảo proved to be much more successful as the first series had a production of 27,629,000 coins while the second series greatly exceeded this with around 200,000,000 coins produced in Huế, Haiphong, and Hanoi. The Khải Định Thông Bảo continued to be produced long after the death of Emperor Khải Định under his successor Bảo Đại until it was phased out by the Bảo Đại Thông Bảo (保大通寳) in 1933.

The Vietnamese cash, also called the sapek or sapèque, is a cast round coin with a square hole that was an official currency of Vietnam from the Đinh dynasty in 970 until the Nguyễn dynasty in 1945, and remained in circulation in North Vietnam until 1948. The same type of currency circulated in China, Japan, Korea, and Ryūkyū for centuries. Though the majority of Vietnamese cash coins throughout history were copper coins, lead, iron and zinc coins also circulated alongside them often at fluctuating rates. Coins made from metals of lower intrinsic value were introduced because of various superstitions involving Vietnamese people burying cash coins, as the problem of people burying cash coins became too much for the government. Almost all coins issued by government mints tended to be buried mere months after they had entered circulation. The Vietnamese government began issuing coins made from an alloy of zinc, lead, and tin. As these cash coins tended to be very fragile, they would decompose faster if buried, which caused the Vietnamese people to stop burying their coins.