The First Prototype Boba Fett helmet is often referred to as the Preproduction #1 helmet, prepo 1 helmet, or simply PP1 helmet. It is also commonly referred to as the "Eyes" or "Ears" helmet due to the eye-shaped markings on the top of the helmet.
Note that the eye-shaped marking were moved from the front of the dome of the helmet to the top of the helmet. Faint lines can still be seen on the helmet where the markings were originally located.
This helmet was supposedly painted by Joe Johnston after the decision was made to move away from the all white "Supertrooper" style of costume.
This helmet is a true transitional piece between the original Supertrooper style and what eventually became Boba Fett's iconic helmet. Note that unlike Boba Fett's helmet which has an iconic dent, the First Prototype helmet has a deep gash in approximately the same area.