Lode Shields are items found in Zeal. The Nu in Kajar once sold them before they were outlawed by Queen Zeal. Since there is no shield slot in Chrono Trigger's equipment system, players did not miss out on anything. The shield is probably a complement to the Lode Sword. It's revealed in the retranslation that it's actually "Platinum Armor", or "Lode Armor", meaning it might be the Lode Vest.