This is an example of the octagonal 1915 Panama-Pacific commemorative $50 gold, struck in silver, but without S mintmark. It supposedly was handled along with a companion round example J1973/P2036 by Lester Merkin many years ago. These were listed in Appendix A in the earlier editions of Judd. The photo is a doctored gold 1915-S piece. Photo courtesy of American Numismatic Rarities.