I would question why the rearsight is also 'nickel-plated', as all the original plated pistols I have seen, whether from Webley, Westley- Richards, or even the little pop outs, invariably always have their rear sights blued. The reason being that a plated rear sight would reflect or produce glare.
When pistols are re-plated then the rear sights are invariably always plated as well, always a good guide as to whether the plating is original or not.