Do you have information on a 1776 patrona bavariae coin?

The coin was issued in the German state of Bavaria under the rule of Maximilian III Josef. I believe that "Patrona Bavariae" is Latin for "Patron of Bavaria", and indeed Maximilian was technically the Elector of Bavaria (although the title "King" was given to his successors in 1806).

While there were several coins issued in 1776, my guess is your coin is a Thaler with a portrait of Maximilian on the obverse and a Radiant Madonna and Child on the reverse, measuring 28.06mm in diameter and composed of 83.3% silver (giving it an ASW - Actual Silver Weight - of 0.7515 troy ounces). Examples were produced in both Munich (no mintmark) and Amberg ("A" mintmark), but the value is the same for each. According to the Standard Catalog of World Coins, an example in Very Good condition would be worth about US$15, an example in Fine condition would be worth about US$25, an example in Very Fine condition would be worth about US$50, and an example in Extremely Fine condition would be worth about US$100.