consisting of 29 stereo images of crystal structures and crystallographic instruments to illustrate the results of X-ray crystallography by Sir William and Prof. W. L. Bragg printed by Adam Hilger Ltd, London with index card with an original typed letter signed Bragg which reads 'Dear Miss Hepple, I have some old stereoscopic sets of crystal models which have been lying about collecting dust for some years, and i am sending you one as a Christmas present in case it may help you get what you want' dated Dec 31st 36, on headed paper from Professor W. L. Bragg, The Physical Laboratories, The University, Manchester Footnote: Sir William Lawrence Bragg, Kt, CH, OBE, MC, FRS(31 March 1890 – 1 July 1971) was an Australian-born British physicist and X-ray crystallographer, discoverer, in1912, of Bragg's law of X-ray diffraction, which is basic for the determination of crystal structure, he was joint recipient (with his father, William Henry Bragg) of the Nobel Prize in Physics in 1915, "For their services in the analysis of crystal structure by means of X-rays", an important step in the development of X-ray crystallography. Bragg was knighted in 1941, and was the director of the Cavendish Laboratory, Cambridge, when the discovery of the structure of DNA was reported by James D. Watson and Francis Crick in February 1953