Hi Toni, Lischkeia argenteonitens and L. undosa are both valid species, and fairly similar in shape, though the former species is much lighter in weight. However, the outer layer of L. undosa is usually white, and not pearly (nacreous). L. argenteonitens sometimes seems to have a very thin whitish layer overlying the pearl, but other times the white is missing and the pearl is actually outermost. Both these species are fairly uncommon. If you got a gift as a child, which someone picked up in a tourist shop somewhere, I suspect another alternative. There is a species names Lischkeia alwinae which is white like L. undosa, though not as heavily sculptured. It is abundant around Taiwan, and is exported by the thousands for shellcraft and tourist sales. These are sometimes "pearled" - the outer layer removed by acid and/or buffing. One of those "commercial" pearled L. alwinae could be what you have. If you can scan a picture of it, folks on Conch-L can probably give you a positive ID. Regards, Paul M.