Now HERE's a rare look at something!
This is a Sally Acorn mask. It looks like a full head rubber, possibly latex mask. In the first image, it's on a plastic stand, being displayed (likely) at Segaworld Sydney. In the 2nd, that's what it looks like when you put it on. (An actual produced/bought mask worn by a fan)

Remember, Segaworld Sydney was wild about Sally for whatever reason, and they were the ones with tons of official merchandise with her on it, Sally-only items, and even a mascot suit of her. This mask is actually pretty much amazing. The likeness is REALLY good considering it's basically hollow rubber. She's not scary, mutant or absurd. It looks like the character from the show.
There is some debate as to whether this got made or not. Some SWS stuff DID get made but is just so rare it's barely ever seen. Other items were photographed, but never produced past prototype. In the case of this mask, it looks like there's at least 2.