I have a [Ragless] piece that was in my mystery pile. I bought it from the lady across the road who had been given it by her sister in law:

I think I may have solved the puzzle... I received this email from Peter Rowe (Coober Pedy Pottery) after asking him to help with identifying this mystery potter. I have several of these items myself but came across a photo online with the signature - J Ragless and the Coober Pedy Pottery stamp.

Here is Peter's reply...

Hi Karen

Yes I do know this work and it is made by a lady called Jacky Ragless.
She is a lady that started of doing pottery in Brighton SA and eventually ended up in Gawler SA.
She also used to come up to Coober Pedy and do work with me in my Underground Pottery.
She is a very good potter but unfortunately no longer does pottery.
Hope this is of help..

Cheers
Peter Rowe

Fabulous! Another Mystery solved. Great job Karen.