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deleted
478 Posts |
 Posted - 01/02/2009 : 08:17:32
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Counterfeiting Methods
Casting
One of the oldest methods used is the casting of fake coins. Here a mould ismade from a genuine coin. It is usually made in two pieces that are held together while the molten metal is poured in through a small vent, usually placed on the rim of the coin. Alternatively wax models are made from the first mould. These wax models are then encased in a plaster substance, once again with a small vent for the molten metal. When the plaster is set the wax is melted, poured out and the metal poured in. The plaster is broken open to release the fake. Generally cast fakes are of poor quality and easy to detect.
Look for the following telltale signs:
Poor Surface
Air bubbles trapped in the casting or mould material are difficult to remove and will produce a surface that is dimpled or rough. This is usually most common near lettering or places of high relief. Raised lumps and lines are caused by chops and scratches n the genuine coin used as the master or by imperfections in the mould. A cast fake will lack definition. The edges of the lettering and where the lettering meets the field (the flat, background surface)
will be softened or rounded.
Size
As molten metal shrinks when solidifying a cast fake made from a genuine master will be slightly smaller in diameter and thickness.
Edge Imperfections
It is difficult to reproduce the edge of the fake exactly due to the shrinkage. Particularly with a reeded edge coin the vent where the hot metal is poured into the mould will usually show as a blemish. It is possible, however, to cast the fake to a slightly larger diameter and machine it back to the correct size. If the reeding is rolled on by machine after casting it may overlap.
Die Struck
This is the method used by official mints to produce genuine coins. Fakes made in the same way are the most difficult to spot. Genuine Krugerrands are made as follows: 99.9% pure gold is melted in an induction furnace. A small amount of pure copper is added to produce the 91.7%/8.3% alloy required. This alloy is poured into billets 12 mm thick, which are then rolled into strips of the required thickness. Circular blanks are punched out of the strip and tumbled in a soap solution to remove the sharp edges. The blanks are
checked for weight at this point. An upsetting machine (by striking the metal on the edge) gives the blanks a rim on each side; they are annealed (softened) ready for striking and burnished (polished) until smooth and shiny. The blanks are fed into an automatic coin press where the obverse and reverse dies strike both sides simultaneously to produce the required designs. While this takes place the blank is held in place by a collar containing the
reeded (milled) edge design which is forced into the edge of the coin at the moment of striking. The manufacture of genuine coin dies is a multi-stage process whereby the original large scale design (usually in clay or a plastic compound) is transferred to the final dies used for the actual striking of the coins.
Stolen, reconditioned or forged dies are used to mint fake coins. Once a good set of dies is available the actual minting (or striking) of fakes is a relatively simple process and large quantities can be produced in a short time. One modern coin press is capable of producing 50 Krugerrand size coins per minute.
Forged dies can be made in a variety of ways, the most successful being by means of a copy engraving machine (or pantograph), electrical discharge machining or one stage die casting. Any small imperfections on the surface of the fake die can be removed with great accuracy using the jet honing process, whereby tiny glass beads in a liquid are blown by an air jet onto the surface of
the die. Tell-tale signs of a die struck counterfeit are usually a result of a die imperfection as follows:
Working Marks
Removing imperfections on a die is a skilled process. A scratch on a die will appear as a raised line on a fake coin. The electrical discharge machining sometimes leaves minute pitting in the die. They produce small sharp bumps when the fake coin is struck. The unskilled jet honing of defects can leave a rippled die surface.
Lettering
Any imperfections in a fake will usually show up in the lettering. It should be crisp and clean with no haziness.
Marks and Indentations
The field should be smooth. Suspect a coin whose field has marks, scratches, indentations or shows any sign of disturbance.
Tracing Tool Rings
When cutting a counterfeit die certain tracing tools follow the contours of the master coin as it rotates about its axis. This can leave circular rings in the field which must be polished out. Therefore be suspicious if you spot concentric rings.
Edge
Check the reeding or the lettering of the coin carefully. Both should be regular and clearly defined. This is an area that sometimes reveals an otherwise excellent fake.
Electroplating is the modern equivalent of gilding and uses an
electric current to deposit the thin layer of gold or gold alloy on the coin. The thickness of the layer can be accurately controlled by adjusting the amount and duration of the current. The layer on a fake coin is usually only between 3 and 6 microns thick. A thicker layer could impair the definition of the raised relief on the coin.
The colour of a particular coin type will vary very little from coin to coin. This is due to the small tolerance allowed in the composition of the gold alloy used in their manufacture. In the Krugerrand’s case the alloy is 11/12th (91.67%) gold and 1/12th (8.33%) copper. The copper gives the Krugerrand its characteristic
reddish tint. If the alloy composition is not matched accurately when
electroplating or gilding a coin the colour may vary. Suspect a coin whose colour is different.
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wolvesdad
1000+ Penny Miser Member
USA
2164 Posts |
Posted - 01/02/2009 : 12:47:28
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I'm just curious what the point of these threads are.
Is it to encourage counterfieters?
Make anyone cautious or afraid of buying gold coins?
or _____ ? (I'll let CuproNickel fill in the blank - no pun intended) |
"May your percentages ever increase!" |
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NotABigDeal
1000+ Penny Miser Member
USA
3890 Posts |
Posted - 01/02/2009 : 13:06:37
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Add fuel to the fire from another post?
Deal |
Live free or die.
Plain and simple.
"If you love wealth more than liberty, the tranquility of servitude better than the animating contest of freedom, depart from us in peace. We ask not your council or your arms. Crouch down and lick the hand that feeds you. May your chains rest lightly upon you and may posterity forget that you were our countrymen."
- Samuel Adams |
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Lemon Thrower
1000+ Penny Miser Member
USA
1588 Posts |
Posted - 01/02/2009 : 15:00:26
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| violate copyright laws? |
Buying:
Peace/Morgan G+ at $15.00
copper cents at 1.3X
wheat pennies at 3X
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natsb88
Administrator
USA
1850 Posts |
Posted - 01/02/2009 : 15:10:31
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Alright, I'm not usually one to butt in, complain, or plaster threads with unnecessary "me too!" posts, but do we really need 6 different threads on fake gold coins? They could very easily be condensed into one, or at the most two threads. Not to mention this one in particular approaches a "how-to" for an illegal activity.
Yes, there are fakes out there. Yes, there are ways to alloy materials to get something with the same density as gold. No, it is not a very practical or common practice. Yes, the Fisch thing will detect most of the cheap knock-offs. No, it is not an all-encompassing infallible device.
Good enough? |
Nate
The Copper Cave
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NotABigDeal
1000+ Penny Miser Member
USA
3890 Posts |
Posted - 01/02/2009 : 16:39:52
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quote:
Originally posted by natsb88
Alright, I'm not usually one to butt in, complain, or plaster threads with unnecessary "me too!" posts, but do we really need 6 different threads on fake gold coins? They could very easily be condensed into one, or at the most two threads. Not to mention this one in particular approaches a "how-to" for an illegal activity.
Yes, there are fakes out there. Yes, there are ways to alloy materials to get something with the same density as gold. No, it is not a very practical or common practice. Yes, the Fisch thing will detect most of the cheap knock-offs. No, it is not an all-encompassing infallible device.
Good enough?
Works for me.
Deal |
Live free or die.
Plain and simple.
"If you love wealth more than liberty, the tranquility of servitude better than the animating contest of freedom, depart from us in peace. We ask not your council or your arms. Crouch down and lick the hand that feeds you. May your chains rest lightly upon you and may posterity forget that you were our countrymen."
- Samuel Adams |
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pencilvanian
1000+ Penny Miser Member
USA
2209 Posts |
Posted - 01/02/2009 : 16:46:09
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Forewarned is forearmed
with gold going up in price and more and more people buying gold coins fakes are bound to surface.
A dealer once offered me a Liberty $20 coin but he wasn't sure if it was real, as in a real Liberty $20 gold piece. It seemed wrong to him somehow, the light reflected off the coin differently from other $20 Liberty coins he had seen (no it wasn't proof.)
There will be fakes out there, better to be sceptical than be cheated. |
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Counterfeiting Methods for FAKE Gold Coins
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