I agree with Ottowadigs. If you go to EBAY and type in - skull cross bones pin - and then just scroll down through the pages of listings, you will see many similar pins. Most go for $100 plus complete. Most also are associated with a fraternity or school. Yours appears to have the initials of a person on it but it could be the initials of a school or organization. I believe most of these are from the early to mid 1900s. Although the Knights Pythias have a similar skull cross bones incorporated in some of their pins, I have never seen a pin of theirs which had the skull cross bones by itselft. It is always incorporated in a larger pin. Great Find!