It looks just like Melissa Hastings' face, only it is painted dark red-brown with gold accents.
In "Cat's Cradle", Hanna finds the "Melissa" Mask in the backroom of Hector Lime's studio, and puts it in her bag. Hanna later shows Spencer the mask she stole. It looks like Melissa. They hypothesize three scenarios: Melissa followed Alison there, or Alison followed Melissa, or Melissa and Alison went there together. Hanna gives the mask to Spencer.
In "Face Time", Aria and Spencer follow Melissa directly to Hector's shop, and they see Melissa dragging a large sack out of the shop. Spencer later goes to confront Melissa, who is seen breaking the castings of her face and throwing them into the lake. Later, "A" apparently fished the broken castings out of the lake and is seen gluing them back together. It is still unknown if "A" has a plan of using them.