The pick is a +3 Gnomish War Pick of Puncturing that does change size for the user. I should note that you have to be proficient in it for it to change size. It is an exotic weapon that for a medium sized creature is 2d6, 19-20, x4.
It does have gnomish artwork on it, although faint. It is made of what Wignston calls stainless steel. It is around 500 years old.