I think your pottery was made on Catalina Island, 25 miles off shoreof Los Angelos. Owned by the chewing gum magnate Wrigley he wanted the people who lived there to have work. So he built a Pottery co. and a casino in 1929, using the minerals and brown clay from the island. The pottery sold to tourists in the casino and all the gift shops and the mainland. The problem was the brown clay it was crumbly and did not hold up. So they imported a harder clay and it became expensive to buy. In 1939 it was sold to mcGladding & Bean co on the mainland. They used many marks even letting employees mark them. Most were marked Catalina Island many were using other marks. I noticed what looks like a C over and I plus the circle. Mostly all their item were marked using a circle to represent a island. Now it could be another pottery but this is what I think from the info i collected in my Calif. pottery books.