Watch List notes:

Potosi, Bolivia, cob 4 reales, Philip IV, assayer R (Ramirez, 1646-8), extremely rare.S-P31; KM-17a; Cal-unl (Type 279).10.39 grams.Nearly full shield and cross (peripherally flat) with bold full P-R to left (one of very few examples still in existence, as scandalous assayer R's coins were mostly melted), with edge-split and light surface corrosion but not enough to account for such a low weight (probably debased), otherwise Fine, with brown sediment in crevices.
($350-500)