This is a Johnston Bros England Flow Blue, scalloped edge, dinner plate.
Flow blue is a style of white earthenware, sometimes porcelain, that originated in the Regency era, sometime in the 1820s, among the Staffordshire potters of England. The name is derived from the blue glaze that blurred or "flowed" during the firing process.
The
backstamp indicates a post-1913 date of origin.
The factory was in the Charles Street works, Hanley, Stoke-on-Trent from 1883 to 2004.
Jenny found this piece in the local BSL recently. The linked article on Flow blue indicates that most English potteries stopped doing Flow blue in the mid 1910s, to the plate may date from around that period.