Four specimens of isotopically labelled B12 vitamins, c. 1950. Mounted on the original (1950's) display card, 29.5 cm x 13.3cm bearing the legend "The specimens of radioactive vitamin B12 factors contain the following radioactive isotopes (all produced in the atomic pile at Harwell):" 4 glass tubes 6mm O.D. 4.5cm long, corked, labelled (L to R): "Cobalt-60", "Phosphorus-32", "Carbon-14", "Sulphur-35" (not radioactive) isotopically labelled vitamin B12 in the form of small quantities of a dark red powders, by Harwell, British, 1945-1960.