The 10/31 is a mask made by Nikos of NAG and Jimmy Falco of Spookhouse Props. Jimmy acquired a very old Don Post Studios mask, likely to be an early variant of the kirk. All features remain consistent with an original 1975 Kirk with the exception of larger eyes and more human ears. Nikos then retooled the mask to have 75 Kirk eyes and ears, then Jimmy produced them, thus giving us the "10/31".