.375 is 9ct gold (I have a ring with the similar hallmarks).
As far as maker mark goes, I would venture "William Philip Whiteman" http://www.silvermakersmarks.co.uk/Make ... WR.html#WP even though his mark does not feature the & S. A lot of companies did add their sons on later on. The reason I guess him is because he is listed to have done a fob medal before on this site.