What if Armor wasn't represented by a number, but by a code? To some degree that was the original intent of Armor Class.
Page 38 of the 1st edition AD&D Player's Handbook has an interesting artifact left over from Chainmail that is the Armor Class system. I don't recall ever actually using this in play as it is too cumbersome and didn't seem worth the complication for whatever game play it is supposed to add. Today we think of AC as an ascending (or descending) number representing improved defense against weapons, and that is true to an extent. More specifically AC represented a specific type of armor which some weapons were better or worse against as shown on the Weapon Types table.
This concept comes from the Man-to-Man Melee Table in Chainmail (this is my cleaned up reinterpretation of that table):
Taking notes from that idea here is a further extrapolation of the concept, grouping weapons into classes by their similarity. A Weapon Class. So the number does not represent offensive or defensive strength so much as a short hand or code for the weapon/armor it stands for. They could just as well be called A, B, C instead of 1, 2, 3.