Hartill (GCC, p. 115) places this unattributed Vietnamese Càn Nguyên Thông Bảo coin among his category: ‘Large Copper – Others’. HCR 58926 belongs to this type. The metal is visibly reddish copper-rich alloy. Hartill (op. cit.) quotes an assay of Cu 52%, Zn 38% and Pb 7%. Thierry (CMV, CMVS) does not mention these coins.