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The shop was busy and was not charging me for testing so I did not ask. I think they would have tested for more trace elements but I did not know what else to ask for (I should have asked about gold)...anyhow I think this result makes it a Class 2, yes?
Posted 05/20/2015 1:12 pm
TJsCoins If you have a 1/100 of a gram scale do the SG anyway - it will be accurate to 1 decimal point or about 6% to 10% of silver content and it will disclose the density of the entire coin. XRF tests (handheld unit) only do the surface readings to a depth of 1 or 2 microns. Laboratory units can read some elements to 100 microns but that is still only 1 hair thick. A thick Sheffield plate (0.003 or more) made in the UK is often sterling silver .925 but the core is pure copper. The weight of the coin can be correct but the density will be very low. The better grade scale is only needed when results better than 1 decimal place are essential. I use an inexpensive scale as a preliminary screening tool to hunt for counterfeit coins.
The request to file the edge reflects an understanding that over time some silver coins will experience surface enrichment as a result of the corrosion of the surface copper. This is particularly true of a lengthy period of time in salt water. Copper is reactive and surface atoms will be eaten away leaving a higher proportion of silver. This is one reason why the "cleaning" of a spot can be helpful. The Lab unit can get beneath that surface depletion area and produce a closer to correct result.
The Class of the Coin is still undetermined. A quick SG will rule out Class 1 because those coins by definition have densities of 10.0 of less. If the SG confirms 10.3 - the coin is either a Class 2 or genuine. The surface features and the edge point to Class 2 not a genuine coin. So you are closing in.
A lab XRF that tests for gold at concentrations of 100 ppm would be able to determine if the coin was made with silver refined before or after 1870. That would be absolutely conclusive.
The request to file the edge reflects an understanding that over time some silver coins will experience surface enrichment as a result of the corrosion of the surface copper. This is particularly true of a lengthy period of time in salt water. Copper is reactive and surface atoms will be eaten away leaving a higher proportion of silver. This is one reason why the "cleaning" of a spot can be helpful. The Lab unit can get beneath that surface depletion area and produce a closer to correct result.
The Class of the Coin is still undetermined. A quick SG will rule out Class 1 because those coins by definition have densities of 10.0 of less. If the SG confirms 10.3 - the coin is either a Class 2 or genuine. The surface features and the edge point to Class 2 not a genuine coin. So you are closing in.
A lab XRF that tests for gold at concentrations of 100 ppm would be able to determine if the coin was made with silver refined before or after 1870. That would be absolutely conclusive.
