Watch List notes:

Mexico City, Mexico, cob 4 reales, Philip II, assayer O below mintmark oM to left, error with no denomination (blank) to right, unique(?), NGC XF 45. S-M11; KM-unl (36 for type); Cal-unl (Type 158). 13.59 grams. In all the experimentation with the positioning of the mintmark, assayer and denomination (which by coincidence also happened at Lima at the same time under assayer Diego de la Torre), apparently the engraver forgot to punch the denomination into the obverse die for this coin, the first of its kind we have seen or heard of, and it is also a choice piece, with perfectly detailed full shield and cross-lions-castles, the legends somewhat flat on a broad flan, the surfaces faintly lustrous under very light toning.
($500-1000)