I figured out the use for Golden and Trashy Tiaras.
Apparently they are meant to be disassembled in order to gain forging materials.
Golden Tiara = 1 copper, 1 iron, 1 mythril
Trashy Tiara = 1 Bone, 1 Eyeball, 1 Humour, 1 Feather, 1 Scale, 1 Fur, 1 Leather, 1 Fang, 1 Carapace, 1 Screw, 1 Seed