Guatemala, 8 Reales (Redondo), Carlos II, 1683, Potosi mint, engraver V (Pedro de Villar), countermarked at Guatemala. Indigenous cast to run in Central America, with Guatemala countermark (type II, radiant Sun over three volcanoes) of 1839. Pierced at 12h (as usual), very good quality nonetheless, charming brownish toning. Quite rare.
The countermark seen on this coin, applied in 1839, was used in a time when the countries of Guatemala, Honduras, Costa Rica and Nicaragua were trying to form a new country after their own revolution, a fictional "United States of Central America". The effort failed completely, but since they had the need to convert whatever currency, metal, old, new, legal, counterfeit, or foreign coin that came to their hands, it resulted in many cobs - originals and counterfeits - being countermarked, just like the coin above.
This mark, on redondo pieces (presentation coins, struck on perfect - or at least the closest they could get to perfection - flans, with special dies; struck to be presented to the viceroy and King of Spain), is rare, even if on cast coins.