This is an example of the round 1915 Panama-Pacific commemorative $50 gold, struck in silver, but without S mintmark.
It supposedly was handled along with a companion octagonal example J1971/P2035 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.