From the 1973 horror film 'Ssssss,' starring Strother Martin and Dirk Benedict, this is a full, foam latex 'snake-man' mask used for the film.
In the film, David (Benedict) is hired by Dr. Stoner (Martin) to assist with his experiments, which includes a serum that turns people into King Cobra snakes. This mask was screen worm by Dirk Benedict during the snake transformation process as David is injected with the serium and begins to change.
