Vietnamese large Minh-mang thong bao coin

Diameter 46.2 mm, weight 21.7g, bronze
Obverse (right image) bears legend of XIXth Century Vietnamese coin Minh Man Thong Bao.
Once more Minh-mang thong bao
Nice additional information about such coin series can be found at Mr.Y.K.Leung site.

Any additional information would be highly appreciated.
Vladimir Belyaev .
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