The pure gold bar is an unused item related to the 2019 Easter event. It appears that it was going to be obtained at some point during the Crafting guild portion of the quest, where one is purifying the gold ore (potentially before or after obtaining the crushed gold pieces, another unused item). However this appears to have been changed shortly before release, as the player simply crafts the gilded imperial egg base directly from normal gold ore at the quest's furnace - yet the item remains in the game cache.
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