It is possible that the two small circular marks found on the inner rim of the base are duty marks, possibly birds, used in Mexico in 17th Century. The larger of the two marks impressed on the inner rim is clearly crowned and elongated. This may then be the assay office's mark of Mexico, found in the same period. The smaller of the two marks formed as a square punch incorporating two rows of letters is then consistent with the assay master's initials of the same period.