Tom DeLorey had photo-authenticated Mary's coin as having a Missing Reverse Clad Layer, based on her image and the weight and physical appearance data she provided. Mary eventually decided to send the coin off to NGC for grading, and it came back authenticated and graded MS-64. She put it up for auction on eBay in a beautifully well-done Category Featured auction, and it was only by a stroke of bad luck (in my opinion) that she only got about $1,300 for it; someone else listed another Missing Clad Layer Washington Dollar error coin, also graded by NGC, a couple of days after hers. The other coin, however, only sold for about $870, primarily because it wasn't Featured.
The obvious lesson here is that if you have a major error coin to sell on eBay, spring for the $30 bucks or so to make it visible to your potential buyers.