Artisan Archive

I've heard some debate, but couldn't find it. So, what item is best at grinding that experience from Eng IV to your favorite crafting specialty? Weapon powerups give 40 gcxp for 10 units. But that is around 500 items or more to make. I don't know exp for bone armor, but there is little need for this lately. Seems the market is saturated with powerlevelling crafters.