Heat shield test block material of the 1966 Apollo Command Module, 6 x 2 x 4, bearing a small metal plaque engraved with the text: “Test Block from Heat Shield of Apollo Command Module 1966.” The block is stenciled on the top with part numbers, “AVCOAT 502-39HCG, F6-80058-3,” and a date stamp, “Jul 9 1966.” In fine condition. Developed by AVCO Corporation, with integration into the Command Module's Thermal Protection System by North American Aviation, the block is comprised of an extremely lightweight fiberglass honeycomb which is hand filled by air gun with the ablative resin material. These heat shields were designed to withstand temperatures in excess of 3200°C. An interesting relic representing the innovative materials and design processes developed during the Apollo program in man’s quest to reach the moon.