Watch List notes:

Potosi, Bolivia, cob 8 reales, 1651/0 O, with uncommon crown-alone (Mastalir K1d) countermark on cross, very rare, Mastalir Plate. S-P35; KM-19b; Cal-unl (Type 327). 25.21 grams. Choice coin on a broad flan with only light corrosion near edge, nice full shield and cross, full P-O and 8-O, full 51 of date with clear 1/0, upper half of deeply impressed countermark at bottom of cross, nicely toned all over. The overdate 1651/0 is quite rare--in fact this is just one of two examples known--and the countermark is also very rare, with just three known in the 8R denomination. Pedigreed to the Roberto Mastalir Collection of Countermarked Potosi Cobs, Plate Coin (page 117 in Part A and page 243 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 original MAREX photo-certificate. From: Maravillas, sunk in 1656 off Grand Bahama Island
($700-1000)