There are four separate knightly classes in for honor, conquerors, wardens, peacekeepers and lawbringers. Added to this each class has dozens of different variations on their armor. The conqueror alone has helmet variations that range from the roman imperial age Cassis Crista to typical 12th century enclosed helmets and strictly ceremonial versions with cumbersome and directly dangerous decorations.

While most types of armor shown are largely based on some manner of full plate armor (with the exception of peacekeepers) they are generally not typical of any particular era, nor are they historically accurate. Like a lot of fictional armor they are often over-sized and frighteningly ornate with impractical details that serve little or no purpose.

TL;DR - The are inspired by armor from just about every era of human history and proper representations of absolutely none of those eras.