Originally sailed for by the Six Meter Class, International Rule Rating starting in 1931. The trophy was donated by Donald W. Douglas, and was named after his yacht, ENDYMION, which was built for him.
SCYA has a letter on Douglas Aircraft letterhead, dated March 8, 1950 from Donald Douglas allowing SCYA to change the deed to match the event to be raced.
Changing the Summer Series to the Cal 32 Class Midwinters.
Redeeded in 1984 to the SCYA Prince of Wales Challenge winner, removing "the winner of the Half Ton Class at the annual Midwinter REgatta" .