Any ideal what may had caused this Cypraea Tigris

[dave r]

Ho Richard, it looks to me like the outer layers of shell have been worn or sanded off the dorsum leaving the underlying juvenile pattern. This was common practice during the 19th century; as the inner shell layers are often very different from the outer ones some unscrupulous dealers removed the outer layers with acid or abrasion and sold the shell as a new species.
Dave