Goldanalytix GOLDSCREENSENSOR Instruction Manual page 31

Unfortunately, this kind of package cannot be measured. The striking and the height of the edge
(especially in case of coins) can lead to a deviation, even though it is not a fake. Always put all
your objects with the front- and the backside on
the device.
Old coins / bars ("old" defined as before World
War II) and especially objects of the 19
may partly differ in their composition. That
means that the gold content is right but the
composition of the remaining amount of some
coins deviates. In terms of .900 gold, those coins
should consist of 900 parts gold and 100 parts
copper. However,
production processes and analysis conditions
those coins are contaminated with foreign
metals which change
Moreover, the gold used for procuding these
coins has not been 100% pure so that further impurities got into the molten metal and finally
into the alloy.
Alloy impurities: The range of possible impurities and their consequences can not be
comprehended entirely. With our testing experience we found, that some Vrenelis 20 CHF
sometimes have 10 to 20 times higher iron content than their cleanly produced "colleagues" of
the same year. The gold content was correct in all of those coins (90%), however besides copper
and silver some coins showed significantly higher iron contents in XRF-analysis. This means that
Vreneli coins from 1922 sometimes were minted inaccurately and that not all components were
controlled properly. Through its highly accurate measuring system the GoldScreenSensor
recognizes those impurities, which leads to lower conductivity values for the measured coins
(iron lowers the conductance of these kinds of alloys). In conclusion to this, old coins that fall
into this category are not to be considered as fake but rather as variations of the coin with
frequent ferromagnetic impurities (iron or nickel). In this case we highly recommend combining
more methods like a density test, gold testing acids or a XRF-test, to gain more data and find out
if the coin contains the right amount of gold (or less, which happens quite often, too) or if its
"just" one of the described cases. A .900 gold coin of course stays a .900 gold coin, even if
instead of the other 100 parts of copper there is 98 parts of copper + 2 parts of iron. The gold
content is therefore not reduced. The conductivity value can therefore change and makes the
interpretation of the results more difficult.
Fine silver coins with a silver content of .9999 (Maple Leaf or Kangaroo) feature a higher
conductivity value than .999 coins. This is due to the fact that even this one per mille of foreign
metal within the .999 gold coins can cause a decrease in conductivity (it of course depends on
the kind of impurity, in case of copper, the effect is not as strong as in case of nickel or iron). This
sensitivity has a particular influence on the aforementioned deep strikings or high edges. That´s
why .9999 silver coins and bars, respectively, are in the range of 62 to 64 MS/m – these values
are beyond the set value of silver, but because of the measurement configuration, this is no
reason to be worried about.
th
century
due to non-optimized
the conductivity.
29