How much is large old Chinese silver tone coin 1796-1820 worth?

China produced hundreds of coins through their different provinces over that time period, so you would need more specific information (date, province, denomination) to gauge a value. Your best bet might be to find a dealer (at a shop or large national coin show) who specializes in old Chinese coins - but do be careful, since true specialists in Chinese are few and far between, and there are a lot of replicas on the market.