Medal of "Palladium Hydrogenium" struck by and presented to Sir J.F.W. Herschel by Thomas Graham in 1869. Label beneath medal inside case states it contains 147 u or 900 volumes of Hydrogen; 19mm diameter, in leather case 4x4x1.5cm. obverse, inscription Palladium. Hydrogenium. 1869. Graham. ; reverse, head of Queen Victoria, profile to left