Medals are like goals that you can aspire to in your time playing. There are three 
types: bronze, silver, and gold. Bronze is the easiest to unlock, except for quest 
related medals that only have gold. There are four different categories: Diplomacy,
Economy, Scenarios, and General inhabitants

Unlockable                   How to Unlock
------------------------------------------
Badge of Honor             - 1k/5k/10k Honor points accumulated (Economy)
Brooch of the High Concil  - Attain the achievement the High Concil (Diplomacy)
Cross of the Metropolis    - Achieve Metropolis statis in an easy/medium/hard map (Economy)
Imperial seal              - Easy/Medium/Hard campeign completed (General)
Medal of Mammon            - 250k/500k/1000k Gold coins accumulated (Economy)
Medal of the Elector       - Win the "Elector" Scenario (Scenarios)
Medalion of the People     - 1k/10k/50k inhabitants settled (Diplomacy)
Metal of the Diplomat      - Win the "Diplomat" Scenario (Scenarios)
Metal of the General       - Win the "General" Scenario (Scenarios)
Metal of the Guild Master  - Win the "Guild Master" Scenario (Scenarios)
Metal of the Imperator     - Win the "Imperator" Scenario (Scenarios)
Navy Cross                 - 15/30/50 ships sunk (Diplomacy)
Nobel Insignia             - 1k/5k/10k Noblemen settled (Diplomacy)
Order of the Keepers       - Attain the achievement Order of the Keepers (General)
Order of the Treasures     - 100/500/999 tons of goods in a warehouse (Economy)
Seal of the Orient         - 1k/5k/10k Envoys settled (Diplomacy)
Time Medal                 - 10/100/500 House on one profile (General)