Welcome to the forum.
Assay office mark is missing, most probably under tin-lead soft solder used to fix thistles (not very professional repair).
Queen Victoria head duty mark.
Date letter looks like 1876 /1877 for Birmingham.
If so, the maker could be Edwards & Ball of Birmingham (registered 1839).
My assumption, assay office missing, is based on the shape of date letter and lion passant at the time.