I won this Vulcan hat in week 107 of the IAW Star Trek auctions on eBay. Hats like this one were first seen in ST III: The Search for Spock.
This particular hat is unique for two reasons. One: I cannot recall ever having seen one of these "sideways" hats before. Most Vulcan hats have a jewel on the forehead. Two: This is the only one of my three Vulcan hats I have received on it's original styrofoam storage head. There is a number (3-11) on the head which corresponds to a Paramount tag in the hat. I assume this was so they could match it to a particular costume or actor. Hopefully I'll find a costume labeled 3-11 someday.
UPDATE: As of July 10, 2010 this item is no longer in my collection. I sold it to forum member, Carolan.