. Bulletin - United States National Museum. Science. Fig. 54.— ItN-DuLiAR CJoLD Piece issued about 1849 by J. S. Orsmby & Co. in Sacramento, California. medals. Deceptive centrifugal casts may be readily ascertained and eliminated tiirough this method. This was demonstrated in tests conducted in coopera- tion with the United States Secret Service and the Bureau of Standards. X-ray-back-reflection patterns of two United States 1-dollar gold pieces showed definite differences as can be seen from the juxtaposed photographs (fig. 140). The rings on the right are much narrower and less spotty t
. Bulletin - United States National Museum. Science. Fig. 54.— ItN-DuLiAR CJoLD Piece issued about 1849 by J. S. Orsmby & Co. in Sacramento, California. medals. Deceptive centrifugal casts may be readily ascertained and eliminated tiirough this method. This was demonstrated in tests conducted in coopera- tion with the United States Secret Service and the Bureau of Standards. X-ray-back-reflection patterns of two United States 1-dollar gold pieces showed definite differences as can be seen from the juxtaposed photographs (fig. 140). The rings on the right are much narrower and less spotty than those on the left. They correspond to a struck, genuine piece on the right and a cast, counterfeit one on the ;* These experiments are based on the fact that the structure in this type cast metal is crystalline with extremely small crystallites due to the rapid cooling, while the processes in the manufacture of a struck piece induce distortions in the crystalline lattice. These differences of the structure of the metal result in diff"erent X-ra\- back-reflection patterns. In 1964 tests were conducted by the Division of Numismatics in cooperation with the Bureau of Standards to determine metallurgical details in con- nection with a platinum 50-ccnt piece dated 1814, a Russian 3-ruble piece, and two 5-dollar gold pieces issued in 1849 by the Massachusetts and California Gold Compan>-. X-ray radiographic and diffraction techniques were used, and the experiments were USA'.y/ Report, I960, p. Fig. 55.—Five- and 10-Dollar Gold Pieces issued in 1849 by the Pacific Co. in San Francisco. continued in the spectrochemical analysis section of the Bureau of ;" Through the cooperation of the Naval Research Laboratory, it was possible to conduct comparative analyses of an ancient silver quarter shekel, struck during the first year ( 66 67) of the Jewish war against the Romans, and of a silver shekel struck during the third year of the sam
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