Castrol Motor Oil promotional badge by Butler in diamond pattern

A good original circa 1950's 'Castrol Oil promotional badge'; chomium plated example inlaid with green enamel and inset with 'Patent', inscription enhanced with red translucent enamel; the reverse impressed with scarce manufacturer's details 'Butler 48 Vittoria St Birmingham' within diamond dot pattern. Good condition, no enamel loss, some stress marks and minor service wear. Width 33mm. Height 14mm.