In the included October 17th, 1994 dated U.S. Army technical report titled "Development of Anthropometric Analogous Headforms" it states, "The overall goal of the CTI study is to design three manikin headforms ---small, midsized, and large -- for use in military ejection seat and crashworthiness testing, as well as retention and fit assessment, of helmet and head-supported devices." Head circumference both measure approximately 22 inches. Both made of brass, would work well for helmet display heads. They are both very good showing an attractive, lightly aged patina overall with minimal wear.