Placentia Perfection walnut at 1893 World's Fair
I am having trouble finding walnut experts in California that are part of our system.
There is a guy that did the review of the walnut literature on their fruit and nut crop pages, John Preece, Horticulturalist, USDA ARS National Clonal Repository for Fruit & Nut Crops, Davis.
They also have a list of advisors. One might be near you, that you might contact.