Watch List notes:

Costa Rica, 50 centimos, 1923 counterstamp (Type VIII) on a Costa Rica 25 centavos, 1893-HEATON, NGC MS 66 ("top pop"). KM-159. Frosty white with blazing luster, just about as flawless as a counterstamped coin could ever get, currently tied with three others for top honors at NGC.

Estimate: $300 - $600