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Coins & Cleaning


How can one tell when a coin has been cleaned, especially if it was cleaned long ago?

If the coin has been cleaned with an abrasive, the coin will have hairlines. Also, abrasive cleaning often leaves some crud in the recesses of the coin (untouched dirt or left over abrasive).

If the coin has been dipped (Silver) it may or may not be detectable,but it sometimes leaves the coin bright on high grade coins.On lower grade coins you get a light steel grey tone like cloudy milky water. Also dipping can strip the lustre off  the coin, with the end result that there is no lustre where you would expect it to be for a coin in said condition (EF and better coins).

A natural coin has a particular appearance which reflects the history of its storage. Haphazardly stored coins tend to have a "dirty" appearance to the toning. Coins that have lived for a long time in a coin cabinet tend to have spectacular coloured toning. Coins stored in a clean metal vault (such as an old style "piggy" bank) may stay white (or red) for a long time. Coins stored in albums develop either the familiar "ring toning" (slide type albums) or the much less desireable "one sided toning" (all cardboard albums). Coins stored in mint bags often show spectacular rainbow toning, similar to that seen on coins stored in coin cabinets.

Copper/bronze/brass coins that have been cleaned have an unnatural colour, often looking like a toned gold coin. Even after they retone, they tend it tends to be uneven and a slightly odd colour (watch out for dark areas). See that red in the recesses of that VF copper coin? Not a good sign! Naturally toned, *circulated* copper tends to be very uniform in colour, although they might be dark and dirty around the lettering and similar protected areas. Uncirculated copper may tone very unevenly (especially proofs), so do not automatically count this against such a coin.

Exactly the other way around, silver coins that have been cleaned tend to be extremely uniform in colour after they retone, including the tops of the letters and protected areas. Silver coins with natural toning will usually show some variation in the colour at these places. Be aware that a uniform slate grey colour can be produced on silver very easily with a number of chemicals. Finally, a heavily toned and subsequently dipped silver coin will tend to have a grey milk like colour/ appearance caused by surface roughness rather than tarnish. This can be detected by careful examination with a strong magnifier.


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