Reference
Note:
Thierry (CMVS, 2001: 17, 56) regarded this Chính Nguyên Thông Bảo coin as a private issue in Northern Vietnam (Đàng Ngoai 唐外), dating it between 1592 and 1789. He placed it within his ‘Vĩnh Định Thông Bảo’ grouping, noting the characteristic style and pinkish tinge of this series resulting from the high proportion of copper in the alloy.
Reference
Note:
Thierry here refers to this Chính Nguyên Thông Bảo coin by its Chinese legend as Zheng Yuan tongbao, stating that this is an unattributable private issue of the mid 18th century.
Reference
Note:
Hartill includes this Chính Nguyên Thông Bảo coin among the unattributed issues in his category ' Small Copper - Distinct Calligraphy. Group 4 ("Mac Type").