Note: Do not rely on this information. It is very old.
Beaverheraldry
Beaver (heraldry). Though the animal of this name sometimes occurs, the word in Heraldry nearly always is used to signify the beaver or visor of a helmet, which was that part protecting the sight and opening in the front, and capable of being raised or lowered at pleasure. Whether the beaver be open or closed, whether the helmet be in profile or aflrontee, the metal it is made of and the number of "grills" displayed determine, with other marks, the rank belonging to the owner of the coat-of-arms which it surmounts.