Potosi, Bolivia, cob 4 reales, Philip IV, assayer not visible (1620s), 2R-sized castles in cross (unique). KM-17. 13.38 grams. Very thick, round flan with bold full crown and shield and cross, the latter with tiny castles (meant for 2R) and "greyhound-like" lions (per Sellschopp #454), AVF with good contrast from dark toning in crevices.
Estimate: $200-300