$ilverHawk

There are several different ways of doing metallurgical analysis, some are destructive to the piece and some aren't. The non-destructive bombards the sample with either x-Rays or neutrons. In the case of the X-ray analysis the atoms in the sample absorb the X-ray energy exciting some of the electrons to a higher energy state. When the electron return to the lower state they emit photons characteristic to that particular element. The frequency of the photons tell you what the element is, and the relative strength of the emission tells you the amount of the element present.

 

Neutron analysis works similarly except instead of just photons you are looking for other particles as well, neutrons, electrons , possibly even gamma rays, protons and positrons. In each case the re-emission of the elements after they absorb the bombarding neutrons. Again the characteristic energies on what is re-emitted tels you the element and the strength of the emission tells you the amount .

 

X-ray analysis is cheaper and faster but has the drawback that it only tells you about the surface composition down to maybe a couple of microns. Neutron analysis penetrates deeper but takes longer, costs more, and depending on what elements you have present could result in a slightly radioactive sample for awhile.

 

Typically for coins X-ray analysis is used. It used to take special labs and half million dollar electron microscopes to do the anaylsis, but today they now have hand held devices that cost several thousand dollars (That can often be rented for a couple hundred dollars a month) that can take the readings in a matter of seconds. They report the elements present and their percentages. These can test coins right through the holders they are in so you can test a coin while it is still in a slab.

Excellent information. Hand held XRF spectrometry devices are widely used to assay metal content.

See here http://www.bruker.com/products/x-ray-diffraction-and-elemental-analysis/handheld-xrf.html.

There was an earlier thread, on this forum, which I will try to find, that demonstrated that coin composition analysis by XRF spectrometry while very accurate, was affected by TPG holder plastic resulting in some very confusing metalic analysis results. The holder plastic refracted the return signal resulting in false readings of metals present in the sample.

I think Messydesk may have info on this subject.

Carl

A new medal. I found the design to be quite lovely.

 

This medal is a restrike of the medal given to all members of the armed forces who served in World War II. It was designed by Mr. Thomas H. Jones, whose initials can be seen on the obverse at the right base of the female figure.

 

The female figure, Liberation, is shown facing left as though looking to the dawn of a new day, her right foot resting on a Roman war god’s helmet. In her right hand is a broken sword with the blade that was broken off in her left hand, symbolizing defeat of the Axis powers. Visible behind the war helmet is a rising sun with rays.

 

Beautiful Medal. Please excuse me for this off topic comment. Very sad that the various past Administrations and Congresses do not understand, honor and further the values ennobled in this Medal.

Carl

OK, informed collectors are interested in the market grade when evaluating modern coins. So the question becomes if you are comparing equally graded coins and one of the coins has a "Mercanti" autograph, is there any market value added?

IMHO any added value is an artifact of marketing and any collector drawn into the web is welcome to the realities of trying to sell the value of an autograph versus the true market value of the coin.

Best wishes to anyone that buys a coin with a valuation based on anyone's autograph.

Carl

Here we have the newest addition to my Walker Short Set. First *star* Walker I have owned.The photo work is by Coindude.

Picked up a very nice 1829 Bust Half Dollar NGC XF45 form Carl--123cents. Fast easy transaction.

Thanks, Carl