Mermaid's Scale
The Mermaid's Necklace is one of fourteen Trading Sequence items in Link's Awakening. After Link returns the Fishing Hook, the Fisherman in the Under the Bridge area will fish up the Mermaid's Necklace.[1][2] Link can take this to Martha, the mermaid in the northwest of Martha's Bay. She complains that she has lost her necklace, and promises to give him a scale if he returns it.[3] She keeps her promise and allows him to take only one scale.[4][5]
Afterward, the Mermaid's Scale can be taken to the Mermaid Statue once Link obtains the Hookshot. A scale can be seen missing from it, as it is not yet complete.[6][7] He can place the scale on the statue to move it aside, revealing a secret passage.[8] Inside is the Magnifying Lens, the final reward for the Trading Sequence.