Mexico
Carlos & Johanna Cob 4 Reales ND (1542-55) M-R, Mexico city mint, KM18, Nesmith-74, nice XF with an edge flaw between 5 and 6 o'clock. Currently the coins from the late series showing assayer R are thought to correspond to Alonso del Rincon, although some scholars dispute this.
Estimate: 500-700 USD