Jay Richard Attenborough & Co Ltd, 142, 144 Oxford Street, London. Goldsmiths, silversmiths, jewellers, watchmakers. Here's the mark as it appears in Maurice H. Ridgway and Philip T. Priestley,
The Compendium of Chester Gold & Silver Marks 1570 to 1962 (Woodbridge: The Antique Collectors’ Club, 2004).

Not easy to scan this big tome with a flimsy A4 scanner!
Ragrds/carling
.