Who Made This

Hi,
I have this plate that I really love and, as you can see, it has a mark, "db."
I found a db in Britain, David Brown, who is a potter and a db in California, Donald Brashear, who is a potter. They have the same mark. The works that I found for each don't lead me to conclusively determine that is one over the other. I lean toward the American, but can not really be sure. Also, I could be looking at it upside down! It could be "qp!"

Any insight into this would be appreciated.
Thanks,
Sid