Yes, it is authentic even without the backstamp. Often with "Brushstroke" patterns - which is what we call these items where the design is hand-painted in glaze, then fired - it is found without a backstamp or pattern name. Or it may be found on one item, but not another - the item it is found on, of course, serving to identify it.
"Corkscrew Plant" is a name given to the pattern based on its design as no actual pattern name has yet to be found on any of its pieces.
Edward Challinor was a well-known potter in Staffordshire, England during the 19th century. I'm not sure who actually identified his pottery as the maker of this pattern, but he's attributed to it in our database which is usually correct as we strive for accuracy.
If you have any other questions, please feel free to contact us again.