This system remains in place today, with just the year 2000 breaking from the system with a special mark.
For a far more detailed study of the marks found on Osmaston Road pieces, plus the very latest research into the correct order of the date ciphers, please see -"Cracking the Code: dating Derby items from the Osmaston Road factory" This was the trademark of the Derby Crown Porcelain Company Ltd and was used c1877-1890.
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.
In 1894 Wileman began earthenware production in a new earthenware works.