The 1780 St Theresa silver dollar is a Spanish colonial coin that is quite valuable. The exact value can vary depending on a number of factors, such as the condition of the coin, its rarity, and the current market conditions for rare coins. However, in general, a 1780 St Theresa silver dollar is worth several thousand dollars. For example, in September 2021, a particularly well-preserved specimen sold for over $10,000 at a public auction.