These are the standard, curved nameplates as fitted on top of loco splashers. They were introduced in the first decade of the 1900s, and lasted till the end of the GWR. The orange lining was carried only on engines that had the fully lined livery.
Early Great Western engines had plainer, square-ended nameplates without the gold rim, fitted on the side of the splasher. Between the early and standardized designs a variety of shapes and locations were tried, including joint name and number plates (e.g. the Atbara class), and straight nameplates fitted on the boiler (e.g. the Duke class).