Well done with the images.
The date letter is that of 1890. See: http://www.925-1000.com/dlc_chester.html
The maker is a problem as the register that was in use at the Chester Assay Office from 1886 to 1894 is missing, the mark is recorded, but no information to go with it. Period advertisements, catalogues, registrations at other assay offices, etc. may offer a clue.