escutcheon (noun) – shield or plate in the shape of a shield with a coat of arms (= symbol of a country, state, city, noble family, etc.)

Here are some examples of how you can use escutcheon:

The door of the town hall bore an escutcheon showing the coat of arms of the city.
The official symbol of the city was two lions on a gold escutcheon with the text: Peace and Justice.