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Silverhaze2
06-08-2011, 12:26 AM
Are there some coins that are better than others as far as having the least or no counterfeits? Is there even such a coin that is not counterfeited?

do I need more than a +/- 0.01g scale and a set of calipers... and the "real" dimesions and weight?

Ryanferr
06-08-2011, 12:30 AM
avoid china. Test with magnet.

Silverhaze2
06-08-2011, 12:30 AM
I found this while looking around but cant find the least.

http://www.pcgs.com/articles/article_view.chtml?artid=5682&universeid=313&type=1

GloryHole
06-08-2011, 12:31 AM
#1 Rule of Thumb .... Only purchase from VERY reputable LCS/Online Dealers.

#2 Rule of Thumb .... Anything coming out of China should be checked & tested 3 times over

#3 Rule of Thumb .... Panda's are likely the most counter-fitted coin

#4 Rule of Thumb .... If buying in person, take a scale, calipers, and a print out of the true coin specs before purchasing ...

ALWAYS do your DD (Due Diligence) and really research the coins that interest you ... I'd stay away from the bay for Gold Purchases.

Silverhaze2
06-08-2011, 12:34 AM
I also mean just plain bullion not numismatic.

coindog
06-08-2011, 12:36 AM
you need to study known real coins with a good magnifier and learn the details. I never leave home without one, besides the other equipment you listed. fake unc. coins are very hard to do right and easy to spot once you develop a good eye.

prunggu
06-08-2011, 12:46 AM
Are there some coins that are better than others as far as having the least or no counterfeits? Is there even such a coin that is not counterfeited?

do I need more than a +/- 0.01g scale and a set of calipers... and the "real" dimesions and weight?

Buy from reputible dealers; Learn how to test specific gravity when buying from individuals. A .01g scale should be accurate down to about 5g pieces for this.

prunggu
06-08-2011, 12:47 AM
avoid china. Test with magnet.

A magnet for Au? I thought that was an Ag thing...?

Silverhaze2
06-08-2011, 01:00 AM
Buy from reputible dealers; Learn how to test specific gravity when buying from individuals. A .01g scale should be accurate down to about 5g pieces for this.

Is that a fancy term for doing a density test? water displacement and weight
for a gram per cubic cm?

chantgirl314
06-08-2011, 01:18 AM
Many items that are gold filled or plated are magnetic, but not all. If the item IS magnetic, then it is not gold. However, just because a piece isn't magnetic doesn't automatically mean it's gold. I test with a magnet first, then an electronic tester, and finally an acid test. This works well with scrap jewelry, but most coin sellers are not going to allow you to do a destructive test, so there a magnet, scale, calipers and knowledge are the best bet.

One caveat- if a piece of jewelry has a spring ring clasp, the clasp itself will be slightly magnetic since there is a base metal spring inside the clasp. Just because the clasp is magnetic does not mean the piece is fake.

prunggu
06-08-2011, 01:41 AM
Is that a fancy term for doing a density test? water displacement and weight
for a gram per cubic cm?

Density is expressed in grams per cubic centimeter; Specific gravity is the density of a substance divided by the density of water. Since (at standard temperature and pressure) water has a density of 1 gram/cm3, and since all of the units cancel, specific gravity is usually very close to the same value as density but dimensionless (i.e., without any units).

Please note that SG test only works for solid pieces, not hollow. I'm assuming bullion brs or coins here so that shouldn't be an issue.

.999(9) fine gold should have an SG = 19.32

For alloys, you need to do a bit more work as you need to sum the SG of all alloys proportionally. You'll find a list of SG values for basic elements as well as how to calculate SG of alloys at http://www.hauserandmiller.com/reference/melting.html

Here are some calculations I did a long while ago for a couple of the more common .9167 and .9000 bullion coins:


AGE
91.67% au + 5.33% cu + 3% ag

916.7 x 0.051759 = 47.4474753
53.3 x 0.111617 = 5.9491861
30.0 x 0.094966 = 2.8489800

1000/56.2456414 = 17.78 SG

Krug
91.67% au + 8.33% cu

916.7 x 0.051759 = 47.4474753
83.3 x 0.111617 = 9.2976961

1000/56.7451714 = 17.62 SG


Centenario
90% au + 10% cu

900.0 x 0.051759 = 46.5831
100.0 x 0.111617 = 11.1617

1000/57.7448 = 17.32 SG

Have fun knowing your gold!

devilsadvocate
06-08-2011, 01:50 AM
Are there some coins that are better than others as far as having the least or no counterfeits? Is there even such a coin that is not counterfeited?

do I need more than a +/- 0.01g scale and a set of calipers... and the "real" dimesions and weight?

As you know there are not too many things heavier than gold making it hard to fake. You can fake it with platinum but who cares since that is worth even more. Lead can be used to fake silver but not gold. As far as I know the only substance that you really have to worry about is Tungsten since it has a size and weight very similar to gold. I have heard many more reports of gold bars filled with Tungsten than Tungsten coins plated with gold. The only fake tungsten coin that I have heard a rumor about is the Chinese Panda though personally I have never seen an actual picture of one.

I would be very interested to hear if anyone on this forum has ever seen a gold plated Tungsten coin?

Silverhaze2
06-08-2011, 01:54 AM
A magnet for Au? I thought that was an Ag thing...?

Actually there are 3 types of magnetism. Au and Ag are diamagnetic read about it here.. http://www.ndt-ed.org/EducationResources/CommunityCollege/MagParticle/Physics/MagneticMatls.htm

run a neodymium magnet over a PM coin and it'll move.
http://www.youtube.com/watch?v=ClkP-QwIOAQ&feature=related

skip to 1:20... same magnet, from a hard drive.
http://www.youtube.com/watch?v=NgSXg-WOEVY

ArgentAurum
06-08-2011, 02:03 AM
No one is going to tote the equipment to test specific gravity with them to the coin shop, so your best bet is to familiarize yourself with the correct look and feel of the bullion coins you are buying. Get them from a store you know stands behind their coins. A set of calipers and a digital scale is all you should need. Any good coin shop will let you use theirs if you need to check something.

Silverhaze2
06-08-2011, 02:09 AM
Density is expressed in grams per cubic centimeter; Specific gravity is the density of a substance divided by the density of water. Since (at standard temperature and pressure) water has a density of 1 gram/cm3, and since all of the units cancel, specific gravity is usually very close to the same value as density but dimensionless (i.e., without any units).

Please note that SG test only works for solid pieces, not hollow. I'm assuming bullion brs or coins here so that shouldn't be an issue.

.999(9) fine gold should have an SG = 19.32

For alloys, you need to do a bit more work as you need to sum the SG of all alloys proportionally. You'll find a list of SG values for basic elements as well as how to calculate SG of alloys at http://www.hauserandmiller.com/reference/melting.html

Here are some calculations I did a long while ago for a couple of the more common .9167 and .9000 bullion coins:


AGE
91.67% au + 5.33% cu + 3% ag

916.7 x 0.051759 = 47.4474753
53.3 x 0.111617 = 5.9491861
30.0 x 0.094966 = 2.8489800

1000/56.2456414 = 17.78 SG

Krug
91.67% au + 8.33% cu

916.7 x 0.051759 = 47.4474753
83.3 x 0.111617 = 9.2976961

1000/56.7451714 = 17.62 SG


Centenario
90% au + 10% cu

900.0 x 0.051759 = 46.5831
100.0 x 0.111617 = 11.1617

1000/57.7448 = 17.32 SG

Have fun knowing your gold!


my brain caught fire while trying to read that. but, do I have to be that cautious? wouldn't a density test be sufficent?

and unless done in a perfect vacuum... is anything truly not hollow? :D