I wonder if Napco was responsible for Eureka’s pure white attachments and upright handles from the 1980’s. These attachments and handles have yellowed very badly over the years. You can see the severity of the yellowing because they are oftened found along with pure white rubber dusting brushes and bare floor brushes that have not yellowed at all.
Interesting to note that pure white Miele canister bodies seem to be made of a better kind of plastic that never ever yellows.