Rare Sea Shell - Please help with Identification

[paul monfils]

The first picture looks like it could be a sinistral, or "left-handed" specimen of Turbinella pyrum, the Great Indian Chank or "Sacred Chank" shell, which means the shell spirals in the opposite direction from normal shells of the same species.  If so, it is quite rare, and could bring a good price if it is in good condition.  I can't tell much about the condition from this picture. It looks pretty worn from what I can see, but a lengthwise view of the top and bottom of the shell would provide the most information.

Here is a picture of a sinistral specimen and normal specimen of Turbinella pyrum: http://www.jaxshells.org/pyrum1t.htm