California pottery teapot?, signed JCR or RCJ or CRJ, any thoughts.

Does anyone recognise the mark on the base of the teapot. We are pretty sure it is American, and probably Californian, but have not been able to find this mark anywhere in any of our books. I know I have seen this form before, but don't remember if there was a attribution to it at the time. Any and all help much appreciated. We have owned the pot for at least 10 years now.
Thank you
Jack