First introduced in 1963, Moving Mouth masks had a two-piece construction with the jaw attached by metal eyelets enabling the mouth to open and close when the wearer talked.
The design is credited to Abraham Grossberg who transferred the rights to Ben Cooper in 1962. It was patented the following year (link).
Early ads referred to them as “Yak-Yak” costumes, it’s unclear if that’s initially what Ben Cooper called them or if the name was an invention of the newspapers.
The masks came in specially labeled versions of the Magic-Glo (link) and Swirls (link) boxes.
In 1966 the masks were rebranded as “Chattermouth” masks and the metal eyelets were replaced with elastic bands, presumably to lower production costs. A new box was made specifically for the line (link).
Further modifications were made to improve the mechanics of the jaw. The updated design was patented in 1977 (link) and a new box was made (link).
I believe the masks were discontinued a few years later.
VacFace 