GOLDANALYTIX GOLDSCREENSENSOR Bedienungsanleitung Seite 65

Important Information on Measuring with the GoldScreenSensor
Special Cases:
Older coins/bars (defined here as coins/precious metals before World War II) and especially
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objects from the 19 century may vary in their composition. It may happen that the gold content
is correct, but the remaining composition differs for some coins. For example, .900 gold coins
should consist of 900 parts gold and 100 parts copper. However, due to non-optimized
manufacturing and analysis conditions at the time, such coins may have been contaminated with
foreign metals, altering the conductivity of the coin. Moreover, the gold used for manufacturing
was not 100% pure and impurities could enter the final alloy during melting. Due to the possible
impurities and the resulting changes in the conductivity, reliable authentication of older coins
and bars with the GoldScreenSensor is often not possible.
Fine silver coins with a fineness of .9999 (Maple Leaf or Kangaroo) have a higher conductivity
value than .999 coins. The reason for this is that even one per mile of foreign metal in the .999
gold coins can cause a decrease in conductivity. The conductivity drop depends on the type of
impurity: Contamination with copper results in a less pronounced conductivity drop than with
nickel or iron, for example. This sensitivity is most noticeable in coins with deep mintings or high
edges. Therefore, it may happen that .9999 silver coins or bars are in the range of 62 to 64
MS/m – such values are above the target value of silver, but are perfectly fine due to the
measurement configuration.
The effect of the conductivity drop is particularly strong for silver coins with a fineness of less
than 958. Therefore, it is not possible to verify their silver content with the GoldScreenSensor,
especially for typical silver commemorative coins. Rather, it can be ensured that the conductivity
is plausible for silver (>30 MS/m) and the dimensions and weight must be examined very
thoroughly.
Special case Krugerrand Silver 1 Ounce: Our tests have shown that these .999 silver coins can
have values of 55-59 MS/m. This same applies for the "Owl of Athens" and some "Tokelau"
coins, amongst others.
Medals and jewellery cannot be successfully tested by measuring the conductivity. Even if a
piece is completely contiguous and the measuring coil is completely covered, the alloy is not
known in detail. At best, one knows the gold content, but the other unknown components of the
alloy have an unpredictable effect on the conductivity.
Particularities of the 5 DM commemorative coins of the years from 1979 (Otto Hahn) to 1986
(Frederick the Great) – This series of commemorative coins has a weight of 10.0 g (previous
years 11.2 g) and is made of a copper-nickel alloy with a nickel core (previous years silver 625).
These coins show a conductivity of about 2.4 MS/m (nominal value of silver 625 about 47.0
MS/m).
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