The maker is Smith & Bartlam Birmingham Makers Marks - S&-SA
1917.
Silver Cigarette Case: Hallmarked Birmingham 1917 by Smith & Bartlam: Measuring 8cm x 5cm: Weight 54
If the “m” is puzzling you, they also used it in their Chester Mark:
Edward E Smith and his partner William Bartlam of Regent Parade, Caroline Street, Birmingham also registered their mark in that assay office March 1905. It too had a small m after the B. Presumably to differentiate it from Synyer & Beddoes and two other unidentified marks also S&B.
If your cigarette case has a rubber band in it that will vulcanize and stain the gilt inside the case. Either remove the rubber band or encase it with tape.
CRWW
After hours of looking at lions, anchors and letters depicting dates my facial features were close to your welcome photograph. Thank you for being helpful and removing my stress.

