This is a Navajo squash blossom, I would date it 80s - 90s. The stone could possibly be Castle Dome, you don’t see much characteristics besides the really nice blue to give it away. You are right that it is not the work of Anson and Letitia Wallace, this piece might also outdate the couple. It is going to be difficult to find out the name of the artist. Squash blossoms are in, this has a nice vintage look, $750 - $900 range.