TR â€” Your picture shows the general type that regularly turns up in Britain in two sizes, a small one that could be 11cm x 7cm that is unmarked, and is often attributed to Sowerby, and a much larger platter, that could be 11" x 7", that is much more scarce, and might carry the Sowerby TM. If they are Sowerby, that colour dates from the introduction of their Tynesyde
glass in the late 1920s at the earliest.
If you are certain about your family tradition, then the simplest explanation is a replacement for a broken piece.
Religious artifacts are difficult, generally unmarked, and rarely appearing in trade catalogues as they were sold in bulk to religious wholesalers.