Dueling Cloak

[Ryuuk]

In a gestalt game we're going to play, one of my players is gonna try an Elven Duskblade//Beguiler. While looking through Cyrstal Keep, he found this (http://www.crystalkeep.com/d20/rules/DnD3.5Index-Equipment.pdf), specifically the Dueling Cloak. It looked pretty good, it grants a shield bonus and seems to mesh well with the class choice. Would this be a Shield or Light Armor though? It does grant a shield bonus instead of an armor bonus, but it requires Light Armor Proficiency. Would you consider it fair game for both class's Armored Mage ability?

[Shadow]

I haven't seen the entry in Dragon, but in the link you gave it specifically states that it gives a +1 Armor bonus to AC. It says nothing about a shield bonus on the page you linked.
But as I said, I haven't seen the DM entry.

[edit] My mistake. I didn't have my glasses on and I didn't see the notation (3).

By the information provided, I would rule it as essentially being a buckler shield (that just happens to be attached to your cloak instead of your arm).