Realms of Arkania: Blade of Destiny

Your armor rating increases based on the quality of your armor, so you'll need to stop by arms merchant to collect this achievement. There are three pieces of armor that will specifically grant this achievement, those items being:

-Plate Mail
-Plate Armor
-Great Helmet

I personally traveled to Ljasdahl to purchase these items, but it's possible that they're located in other places too. It also costs quite a lot of coin to purchase all three, but you can reload once you've finished if you don't want to waste the coin. Equip all three items on one character (one that can wear the armor, like a warrior) and the achievement will pop!