I happened to drop an old wind up carousel from an old microwave some time ago. Inside was the neatest coiled flat spring I have seen since old clock springs became an endangered species. It appears to be some type of stainless steel since it doesn't rust when exposed to water, and high humidity. I have used it for lift springs in patch boxes, and have split it, and used it to stop the irritating rattle modern single triggers exhibit that pivoted on a pin in the triggerplate. It actually can be browned to some degree, and some bluing solutions knock down the brightness too.
Hungry Horse