Help with I.D please bowl with marks - Joan or John C

Does anyone recognise this potter? there are few marks on the bottom: the number FD423 the name John C and an impressed stamp that I cant make out.  Any ideas at all would be welcome. Thanks

The rectangular stamp looks similar to this one on a William Straites Murray pot - http://pin.it/0SXAEvM - but the rest of it looks like s trial piece, signed John or Joan C

Think you're right that its a trial piece and where you can see similarities with the Straites Murray mark - but I'm not convinced. I will hunt around and find it and take another look - perhaps a different photo. Many thanks for taking the time to take another look at this one.