1879 US $ 5 Gold-Counterfeit Analysis...

Hello,

Yesterday, I ran into this seemingly nice $ 5 gold piece owned by a lady whose husband recently died.

The woman knew nothing about coins and just wanted to get some money for all of her coins since this was in a yard sale environment...

Anyhow, being the always-skeptical buyer I went through the only tests that I thought I could perform on-site with the rudimentary tools routinely carried in my car's trunk.

The first test result that seemed to be a bit odd was that the weight of this coin measured on a carefully-calibrated scale was 8.29 grams instead of the 8.24 grams stated on the CCF coin facts page:

http://www.coincommunity.com/us_gol...lf_eagle.asp

I seemed to recall that the US Mint never would never allow any acceptable tolerances over or above the exact 8.24 grams weight in this case: a fact whose origin I could not substantiate at the time.

1) Did the US Mint ever allow tolerance ranges on the weigh of gold coins?

Then I double-checked the Red Book and found the weight listed as 8.359 grams as oppose to 8.29 grams.

2) Although seemingly negligent why does a difference of 0.069 gram exist here?

I already know that based upon the fact that 24k gold is 100% pure, 18 k gold equates to 75% pure gold: 18k/24K.

Therefore, using the 1879 $5 gold piece written metal composition of 90% amount, found in both of the above sources, and working backwards should not the equivalent karat designation be calculated as:

(24k x 90%)/100% = 21.6 k(karat)?

3) Is this calculation method valid?

I then proceeded to test this gold coin by first scraping the exterior reeded-rim down using a small file.

Then I applied a drop of 22.0k test acid at this ground-down area. Incidentally, I routinely carry in my trunk (while maintaining a 78 degree or below temperature) all of my acids to preserve the potency of the acids to avoid arriving at erroneous results...

I became confused and hesitated with the purchase of this coin because the drop of initially clear 22k acid (before touching this filed-down area) immediately turned into a dark-yellow-tinted liquid drop after touching the coin's surface and subsequently stained a sheet of white paper with this same dark-yellow-tinted color.

My final questions are:

4) Assuming that my above calculations are accurate does this coin appear a true 1879 90% US $5 gold coin or not?

5) If this coin is indeed 21.6 karats, would a 22k test acid customarily dissolve the gold enough to produce the dark-yellow-tinted color being that it is rated as only 0.4 k stronger than the 21.6 k AU (gold) composition of the coin etc.?

6) Hypothetically, should an exact 21.6k-rated acid, only 0.4k weaker than the first 22k acid, also turn into a similar dark-yellow-tinted color liquid after coming in contact with this same coin?

In summary, please answer the above six (6) questions and comment on the authenticity of this 1879 P gold Coronet Head $ 5 Half Eagle and whether or not I should have bought it after all.

Thanks,
mdpmedia