Great stuff as usual, Jeff.
But it's not Santiago, Chile. When I first read it, I naturally assumed Chile. But it's Santiago, Spain.
The treasure story is related to the 1811 Napoleonic War in Spain, when France invaded Spain. Retold in 1844, 33 years after the alleged event.
The area below is Larano, which is bordered by a red line around the small village of Lorano today. That gives an approximate area to search to start with. Yet there are still open paddocks and newer development in the vicinity.
An 1811 20 Franc gold coin's value ranges significantly, from around $1,200 to over $1,500 for common Napoleon issues in good condition (bullion value plus premium), but rarer varieties, like those from the Kingdom of Westphalia (Jerome Napoleon), can fetch thousands, even tens of thousands, depending on rarity and condition, with high-grade examples selling for well over $2,000 and rare errors reaching $28,000+, so professional grading and identifying the mint mark (e.g., 'A' for Paris) is crucial
But before we grab our detectors and shovels and get a plane ticket to Spain, there is a proverbial fly in ointment of the story.
Crow