Shell Oil Company advertising lapel badge circa 1920s

A scarce original circa 1920's 'Shell Oil Company promotional badge'; possibly worn by a petrol pump attendant, in the form large gilt brass shell, inlaid with distinct red and black enamel, the reverse impressed with maker's details 'J.R.GAUNT LONDON'. Very good condition, complete with original buttonhole lapel fitting, no defects to the enamel, light service wear. Height 26mm.