White glass screw-in lampshade (M20 West Didsbury)

White glass globe lamp approx 16cm diameter. The measurement across the screw thread is about 8.5cm; depth of screw-in part is approx 2.3cm. It was attached to a brass wall fitting that has a spring clip rather than a thread. The brass has residual paint and some spots of rust, but it's usable indoors and takes a bayonet bulb. The arm fitting is tightened with a nut.