The number is usually six digits long but can be less. The numbers are recorded in the Official Journal of Patents which is available at the Public Records Office at Kew, London, United Kingdom.
In 1919, after Aynsley's retirement the company name was changed to Paragon China Company Limited.
To complicate matters, some genuine Shelley pieces have no backstamp at all, for example salt and pepper shakers. Bruce Sandie and the Australasian club for their generous assistance in providing research and artwork necessary to the creation of this page.
The UK Club has an extensive discussion of backstamps which they have shared with us.
This page shows many of the known backstamps which were used by the Wileman family potteries to include predecessor companies such as Elkin Knight: forth below are some of the most common backstamps used on Fine Bone China and miniatures.
As noted, many variations of the above exist, usually occurring when Shelley or Wileman added a particular pattern name and/or number to the backstamp.