I'm a weaver and from experienct I know that if you upgrade a Royal Footman's Tunic, you get a San D'orian Tunic (+1) or a Kingdom Tunic (+2). I've been trying to figure out what you get when you upgrade the Combat Caster stuff and have come to the conclusion that the upgraded items have the same name +1 or +2. I suspect the same applies here. In order words, upgraded CP items don't necessarily have to have different names, they can be +1 or +2.
Yes, it's an upgrade of the Royal Squire's Chainmail, and the Royal Squire's Chainmail can be purchased with CP. This is not the only CP item with which you can do this. The entire line of level 15 Kindgom gear (including Kingdom Vest, Kingdom Gloves and Kingdom Boots) are upgraded through crafting using the level 10 Royal Footman pieces, which are purchased with CP in Sandy. The level 34 Republic Armor is an upgrade of the level 30 Centurion Armor which is purchased in Bastok using CP.