The William J. Kroll Zirconium medal presented to J.A.L. Robertson in 1993. The 8 cm diameter, 1 cm thick, zirconium medal is presented in a 15 cm square, 8.5 cm tall wooden case. William J. Kroll was a renowned Luxenbourgish metallurgist famous for inventing the Kroll Process for extracting metallic titanium from ores. He later went on to do pioneering work with zirconium.