Watch List notes:

Potosi, Bolivia, cob 8 reales, 1651 E, with crowned-o (Mastalir O3u) countermark on cross, rare, Mastalir Plate. S-P36; KM-19b; Cal-1491. 18.34 grams. Thin and corroded but with good full shield and cross, two bold assayers, full 65 and clear final 1 of date, bold bottom half of countermark on cross side, a rare countermark that Mastalir points out bears a lower-case o engraved over a previous capital O, traces of which appear on other examples. Pedigreed to the Roberto Mastalir Collection of Countermarked Potosi Cobs, Plate Coin (page 207 in Part A and 198 in Part B) in his book The Great Transition at the Potosi Mint, 1649-1653, The 1649-1652 Crowned Shield Coinage and the Countermarks of 1652 (2021), with Moro/Sedwick certificate. From: Capitana, sunk in 1654 off Chanduy, Ecuador
($300-450)