Posted 01/24/2012 11:24 am
Your dealer was spot on, although a bit flippant about it. It does take some time/experience to get the hang of it. When the blank planchet is smashed between the obverse and reverse dies it does some interesting things to the metal. Particularly with silver there is a cartwheel effect as the metal is pushed outward. The pressure also imparts "luster" or frost to the surfaces (fields and devices). As the coin is circulated there is a "natural" removal of the luster. Your dealer learned through experience what is natural and what is unnatural. Manual attempts to remove contaminants and tarnish will create an unnatural appearance ... and confirm cleaning. Here's a recap of these manual improvement techniques the the subsequent results:
- Dipping in solvents (i.e. jewelry cleaner)- If done just a few times, it's very hard to tell, but frequent dippings will remove the surface layer of metal (luster) and the coin will look like there is no contact wear, but it is dull and lifeless, no luster or cartwheel.
- Abrasion - The most common and most destructive form of cleaning. There are many ways to do this ... wiping, brushing, grinding wheel (extreme). Telltale marks appear predominantly in the fields and usually are in a circular pattern. Wire brushing is normally straight-line.
- Tooling (not actually cleaning, but the end state is the same)- An attempt to restore detail to the devices using an engraving tool. This is hard to ascertain without experience and magnification. Look for details on devices that aren't consistent with overall wear.
What to look for:
Uncirculated coins - Undisturbed luster in the fields and high points of the design. The high points are the first to show "rub" and/or wear; cartwheel effect; a dull-looking coin has likely been over-dipped.
Circulated coins - Hairlines, hazing around devices (inability of person cleaning the coin to completely remove undesirable surface material. They are unable to get it off around the devices, i.e., lettering, hair folds, etc., but the fields appear much better).
The best way to learn is to see examples. Perhaps we should start a "sticky" about coin cleaning with photographic examples.
- Dipping in solvents (i.e. jewelry cleaner)- If done just a few times, it's very hard to tell, but frequent dippings will remove the surface layer of metal (luster) and the coin will look like there is no contact wear, but it is dull and lifeless, no luster or cartwheel.
- Abrasion - The most common and most destructive form of cleaning. There are many ways to do this ... wiping, brushing, grinding wheel (extreme). Telltale marks appear predominantly in the fields and usually are in a circular pattern. Wire brushing is normally straight-line.
- Tooling (not actually cleaning, but the end state is the same)- An attempt to restore detail to the devices using an engraving tool. This is hard to ascertain without experience and magnification. Look for details on devices that aren't consistent with overall wear.
What to look for:
Uncirculated coins - Undisturbed luster in the fields and high points of the design. The high points are the first to show "rub" and/or wear; cartwheel effect; a dull-looking coin has likely been over-dipped.
Circulated coins - Hairlines, hazing around devices (inability of person cleaning the coin to completely remove undesirable surface material. They are unable to get it off around the devices, i.e., lettering, hair folds, etc., but the fields appear much better).
The best way to learn is to see examples. Perhaps we should start a "sticky" about coin cleaning with photographic examples.
