QUANTITATIVE RESULTS OF XRF ANALYSIS OF ANCIENT COINS BY MONOCHROMATIC X-RAY EXCITATION

The analysis by XRF applied to old coins is improved by use of monochromatic X-ray excitation of variable energy. In addition the effects of relief and irregular shape are eliminated. A method of absolute quantitative analysis without any reference standard has been set up. Results of the analysis of 52 early Greek and 4 late Roman empire gold coins are reported.     

THE CHRONOLOGY OF GROUPS OF DIES FOR LARGE ISSUES OF ANCIENT COINS USING MAHALANOBIS DISTANCES*

Discriminant analyses of distances and angles obtained from 25 coins struck by P. Crepusius in 82 BC permitted the correct chronology for five groups of closely-related dies to be obtained by the method of Carter and Frurip. Twenty distances and 15 angles were measured on 10 x projections of the coins which represented five groups of dies separated in time from each other. The use of all or many variables gave poorer results than the use of five to ten variables having a high ‘figure of merit’, defined as the maximum range of mean values for a given variable in the five groups of dies divided by the mean standard deviation of the variable in the five groups. It is recommended that chronologies of ancient coins be determined from Mahalanobis distances by using only variables of relatively high figure of merit.     

THE REMANENT MAGNETIZATION OF ANCIENT STRUCK COINS

Magnetic and other measurements are reported for the Guehenno II Gallo-Roman hoard (56-France) which, amongst several thousand Tetricus antoniniani, contains 275 coins struck with the same dies. The orientation of the remanent magnetization is systematically directed outwards from the obverse confirming the identity of the anvil die with the obverse. The magnetization vector is statistically distributed around the vertical axis giving no indication of the geomagnetic inclination at the time of striking. Consequently ancient struck coins cannot be used for dating. The origin of the remanent magnetization was also investigated.     

ION BEAM ANALYSIS OF COPPER AND COPPER ALLOY COINS

In recent years ion beam techniques have become more and more important since in most cases the analysis of copper and copper alloy coins has to be non-destructive. It is therefore of interest to study the relative advantages of several nuclear methods for a certain type of metal. The results are presented here of a comparison between three non-destructive ion beam techniques: particle induced X-ray emission, proton activation analysis and fast neutron activation analysis.     

COMPARISON OF METHODS OF ANALYSIS OF SILVER AND GOLD IN SILVER COINS

A series of silver coins was analysed for silver and gold contents by three methods—chemical wet analysis, activation analysis and X-ray fluorescence using a point source linear spectrometer (milliprobe). The results indicate that while the X-ray fluorescence technique gives better agreement with chemical analysis for major components the use of activation analysis with automated equipment results in a considerable saving of time and has a high sensitivity for some minor components.     

ENERGY DISPERSIVE X-RAY FLUORESCENCE ANALYSIS OF ANCIENT COPPER ALLOYS: EMPIRICAL VALUES FOR PRECISION AND ACCURACY

Energy dispersive X-ray fluorescence (EDXRF) analyses are compared with neutron activation as well as atomic absorption analyses of ancient copper-based alloys in order to examine their accuracy and to estimate realistic values for precision and sensitivity of EDXRF. The results show that it is possible to obtain reliable data of the surface composition of objects non-destructively. Better results for bulk composition are usually obtained with drill samples where the sensitivity of the method is at least competitive with atomic absorption spectroscopy with flame atomization.     

NEUTRON ACTIVATION ANALYSIS OF ANCIENT BURMESE SILVER COINS WITH A LOW FLUX AMERICIUM/BERYLLIUM NEUTRON SOURCE

Nondestructive neutron activation analysis is by now a well-established technique for the analysis of ancient silver coins. The high activation cross-section of silver for thermal neutrons makes it possible to also use this method with the low neutron fluxes available from an isotopic neutron source. In this case due consideration must be given to minimize the self-shielding effect which is encountered with coins above a few tenths of a millimetre thickness. A simple method for the determination of the silver, copper and gold content in silver coins based on the self-shielding properties of silver alloys of different fineness is described. The method has been found to be useful for the quick routine assay of silver coins for the purpose of their classification. Seventeen ancient Burmese silver coins from three different cultural periods of Burma, and two British coins for comparison have been analyzed by this method.     

STUDY OF ANCIENT GREEK COPPER COINS FROM NIKOPOLIS (EPIRUS) AND THESSALONIKI (MACEDONIA)

Ancient copper coins from the Greek cities Nikopolis in Epirus and Thessaloniki in Macedonia, minted during Roman imperial times (31 BC to AD 268), were analysed non-destructively by proton induced X-ray emission, after removal of the patina. An intercompar-ison study using different analytical methods was also performed on five coins. Eleven elements were analysed quantitatively on all coins. Statistical analysis of the results was performed for their presentation in the form of dendrograms. Finally, the variations in the concentrations of some individual elements from emperor to emperor were examined.     

中国古钱版别研究刍议--兼论宋钱的版别

钱币版别是钱币学研究的主要内容,钱币的真伪和珍稀级别鉴定、鉴赏分类、铸行时代、流通区域的断定等,在一定程度上均以版别为基础。钱币的版别以钱币的形制、钱文、图案、金属成分、铸造技术工艺等为     

AN ANALYSIS OF THIRTY-ONE COINS FROM THE HELLENISTIC PERIOD

Thirty-one silver coins of the Hellenistic period were examined by the particle induced X-ray emission (PIXE) method, and the results incorporated into a wider study of the coins. Some tentative conclusions reached in the study are mentioned, together with an outline of the PIXE method. A number of patterns emerged in the results, the most important being an apparent deterioration in silver content among the later Seleucid and Ptolemaic issues; some high concentrations of particular elements were also noted.     

NON-DESTRUCTIVE RADIOISOTOPE X-RAY FLUORESCENCE ANALYSIS OF OLD SILVER COINS

The paper presents the results of a feasibility study of the application of X-ray fluorescence analysis to nondestructive analysis of coins. Radioisotope sources ⁵⁵Fe, ²⁴¹Am, ¹⁰⁹Cd and ²³⁸Pu were used for excitation and a Si/Li detector with a multichannel analyser for the measurement of characteristic X-ray lines. Silver and copper in Polish renaissance coins have been analysed. Analysis using Ag K and Ag L lines allows one to distinguish between blanched and unblanched coins. The accuracy of the silver determination using Ag K X-rays is claimed to be ± 0.5% Ag for homogenous coins and ± 1.0% Ag for blanched but well-preserved uncorroded coins.