On the cover of the catalog for the Bowers and Merena 2009 Baltimore auction, Nov. 12 to 14, was a coin familiar to numismatists.

Lot 3225 was a Mint State 67 1893-S Morgan dollar, graded by Numismatic Guaranty Corp. It was formerly in the Norweb Collection, sold by Bowers and Merena in November 1988, when the coin brought $357,500, at the time a record price for any Morgan dollar. It later was graded MS-67 by Professional Coin Grading Service and it ended up in the second Jack Lee Collection of Morgan dollars.

As it appears in the color plate in the 1988 Norweb collection, the coin had light gray toning. When it again appeared in a 2008 Heritage auction, it was bright white.

In its 2009 Bowers and Merena sale appearance it is described as "a snow-white example without even the lightest toning to either side."

As toning on a silver coin does not magically disappear, one comes to the fairly easy conclusion that the coin was dipped – a process that involves placing a coin briefly in an acidic solution to remove the toned layer.

Sometimes, dipping can create a positive visual impact, and other times it can rob a coin of its character.

In 2008 the Norweb 1893-S Morgan dollar went unsold at a Heritage auction. At its recent appearance in the Bowers and Merena auction, it carried an opening bid of $390,000 and found no takers.

Even the catalog description, somewhat ruefully, includes comments on the coin in the past tense, referring to the coin as it appeared when offered in 1988, quoting a dealer who declared in 2008 that the "Norweb 1893-S WAS the FINEST."

The only other 1893-S Morgan dollar graded MS-67 sold in a 2008 private transaction for a price in excess of $1 million.

That coin, from the collection of numismatic author and curator Cornelius Vermeule, was described in a PCGS press release as featuring "a moderate mix of beautiful original golden brown, tangerine and pale purple colors."

Perhaps the story of the Norweb 1893-S Morgan dollar can serve as a cautionary lesson about the dangers inherent in dipping coins – dangers that can affect the look and value of a coin.