For what it is worth,
San Giusto a Retenanno is located in a mideival fort in Gaiole in Chianti. You do not need an appointment, and they are very hospitable and let you taste everything they have available to sell.
They make both my favorite Chianti (Riserva) and my favorite 100% Sangiovesse Super-Tuscan -- Percarlo. Their regular Chianti and 100% Merlot -- Ricolma -- are also excellent. They also make the best olive oil I've ever tasted.