What is the value of a 1780 maria theresa thaler coin?

Wish I had logged in for the other coin questions. You like eceryone else need to describe the coin much better. In your case it is at least somewhat understandable but if you got as far as knowing it was Maria Theresa why not tell us the origin. The coin was produced in several countries in several provincial mints. It could be worth as little as $5 and as much as $200,000. You need a pro and in reality maybe 2 if the first one says it is worth something