Shell-Mex and BP Ltd 1956 gold diamond long service badge

A scarce original 1956 fine quality 'Shell-Mex and B.P. Ltd long service gold lapel badge' in the form of a small shell bearing the oil company's 'BP' logo in a sheild and set with with two diamonds above; the reverse impressed with Birmingham 9 carat gold hallmarks for 1956 and maker's details 'AC Co Ltd (Alexander Clark & Co Ltd). Very good condition, complete with single screw post and retaining nut also with 9 carat gold hallmarks. Height 17mm.