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What is a "Spark Erosion Counterfeit"?
MrEureka
Posts: 24,060 ✭✭✭✭✭
Somebody, please enlighten us.
Andy Lustig
Doggedly collecting coins of the Central American Republic.
Visit the Society of US Pattern Collectors at USPatterns.com.
Doggedly collecting coins of the Central American Republic.
Visit the Society of US Pattern Collectors at USPatterns.com.
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n the spark-erosion process, a model coin (usually genuine) is submersed in an electrolytic bath where the coin faces the counterfeiter's die steel. An electrical current is charged through the coin so that a spark jumps across the shortest gap between the coin and the die, thus etching the coin's design onto the steel die.
After both the obverse and reverse have undergone the electrical current process, the dies are highly polished. This is necessary because once the dies have been etched, they remain somewhat pitted. The polishing generally will clean up the fields, but often the design will retain the pitting, since counterfeiters tend not to polish the main devices. Either they are unable to get down into the design, or for time's sake they choose to leave the design elements alone. In either case, these counterfeits are easy to detect, since their surfaces are glassy smooth-resembling a Proof finish-yet their devices are lumpy (remember, the pitting on the dies becomes raised lumps on the finished product). Because the excessive polishing makes the dies sharp, these counterfeits appear to be extremely well-struck, with knifelike edges and rims.
These counterfeits usually are found on small-type coins such as cents and dimes, and on small-sized patterns such as those for Flying Eagle cents and dimes. PCGS has not encountered them on gold coins.
Basically, electricity is hooked up to a coin and a blank die and sparks arcing between them removes metal from the die thus transfering the design. Easily discernable because it leaves pits in the dies which transfers to the coins struck with it. Also destroys the coin being copied.
How about some pictures?
Doggedly collecting coins of the Central American Republic.
Visit the Society of US Pattern Collectors at USPatterns.com.
Specializing in 1854 and 1855 large FE patterns
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<< <i>Thanks, guys!
How about some pictures? >>
There are some pictures in this article.
-Amanda
I'm a YN working on a type set!
My Buffalo Nickel Website Home of the Quirky Buffaloes Collection!
Proud member of the CUFYNA
What most articles fail to elaborate upon is the fact that the dies can be used for either stamping dies OR cast molds. I really think that any article out there on this subject over-simplifies the process and the potential danger to collectors. I have seen this process done in person and in great detail.......from start to finish. It can be scary. You will note that in the PCGS article posted by ziggy, they claim that they have not seen spark-erosion counterfeits done in gold. That's because they are often more refined than other spark-erosion counterfiets, or EDM counterfiets, which is the term I use most often. EDM stands for electro-discharge machining. It is an old process. I have seen slabbed gold coins that were created through the EDM process. You would not be able to tell the difference from the real thing.
screw those
waht i reqally want to know is the edm counyerfeit
link
This is not the only vision system out there. I recall seeing them at a trade show 10 years ago. CNC sinkers have been around many years longer.
Heres a system with integrated software. There are several to choose from.
link
<< <i>The coin being copied is destroyed in the process >>
-Amanda
I'm a YN working on a type set!
My Buffalo Nickel Website Home of the Quirky Buffaloes Collection!
Proud member of the CUFYNA
K S
<< <i>Also destroys the coin being copied. >>
Many spark erosion dies were made using modern coins worth only face value in order to produce mint errors such as double struck coins.
Worry is the interest you pay on a debt you may not owe.
<< <i>And heres where the cad models come from. Technology has come a long way since the article on edm fakes was written, or the writer is unaware of just whats out there.
This is not the only vision system out there. I recall seeing them at a trade show 10 years ago. CNC sinkers have been around many years longer.
Heres a system with integrated software. There are several to choose from.
link >>
Jimjenson, I know exactly where you are going with this and you are correct. I have hands on experience with this process as well. A coin can be scanned with a laser at a very tight X-Y grid. The resulting output is an incredibly dense 3D point cloud. This point cloud (really a conglomeration of X-Y-Z points in space) can then be used to make any number of rapid prototypes (molds, dies or the parts themselves). You can also use the data to CNC machine tool steel to make a stamping die, although the machining of such intricate data is not easy. That's why EDM or spark-erosion is more popular. It's Just less time consuming. Also, EDM does not necessarily destroy the host coin. It depends on various factors. It will, however, damage the coin, but you would still have the genuine example after the dies are made.
What is now proved was once only imagined. - William Blake
In 2000, the original coin would not have to be used as an electrode. The end results would be considerably better too. I would imagine it would be possible to crush (coin) silver kennedy half into any other half with the same weight blank, providing you had a surface file and access to a decent CNC Sinker EDM to burn the cavities.