Just saw this http://www.sporting-antiques.com/ Scroll to bottom of page:


"WEBLEY MARK 2 SERVICE RIFLE CADMIUM PLATED
MARK 2 WEBLEY SERVICE RIFLE IN .22 .THIS RIFLE IS CADMIUM PLATED FOR USE IN TROPICAL AREAS TO STOP RUSTING TO THE METAL WORK."

I don't know if this was a factory plating or aftermarket, looks interesting though