The Minh Mạng emperor issued an imperial edict in 1837 stating "it is ruled under the terms of the law that the large monies of brass bearing moral inscriptions will have the value of a Mạch.

[4] These larger cash coins with "moral inscriptions" (美號, mỹ hiệu) were issued under the emperors Minh Mạng, Thiệu Trị, and Tự Đức.

These coins were established by an edit in 1837, which stated that their manufacture should be entrusted to a commission composed of four representatives from different government agencies, one from the Ministry of Revenue (戸部, Hộ Bộ), one from the Ministry of Public Works (工部, Công Bộ), one from the Censorate (都察院, Đô sát viện), and one representative from the Imperial Guard (侍衛, Thị vệ).

Examples of inscriptions used on 1 mạch Minh Mạng Thông Bảo (明命通寶) cash coins would be Trung hòa vị dục (中和位育, "Balance and harmony, all in place, multiply"), Quốc Thái Dân An Phong Ðiều Vũ Thuần ("Country Prospers, People Content, Wind and Rain Plentiful"), and Nguyên hanh lợi trinh (元亨利貞, "The primordial exerts his influence, propicious and virtuous").

Ngoại Tĩnh ("To enrich the country, to strengthen the army, both the interior and the exterior are at peace and calm") despite the fact that Vietnam was suffering from large economic and military deficits at the time.

The main motivation of the government of Đại Nam to adopt this new system was purely to make the coin casting process more profitable, while the Tự Đức Thông Bảo cash coins of 6 phần or 9 phần cost much to make, the Tự Đức Bảo Sao cost significantly less for the same (or even higher) nominal value.

[7] Despite the politicians calculating large profit margins on the Tự Đức Bảo Sao, they did not expect nor foresee that the general population would show widespread defiance to the new high-denomination cash coins.

Afterwards a large number of Tự Đức Bảo Sao would still appear in the hands of private businesses such as metal founders, market stands, and antique shops selling them to Europeans, especially in Hanoi they were often displayed.

[7] François Thierry de Crussol notes how all these cash coins are made from roughly cast brass and aren't properly trimmed.

According to the letter the order was given to mint a new series of Tự Đức Thông Bảo cash coins with moral maxims, the total amounted to 36,133 pieces.