It's my understanding, from an experienced Elsie smith, that extractor forends were blued, and ejector forends were color cased. Is this historically correct?

Thank you.

Forend iron was case colored on higher grade and ejector guns; extractor 0, 00, Ideal and Field were Nitre Blued.

This album has high original condition examples, mostly courtesy of Skip Dunlap
http://www.picturetrail.com/sfx/album/view/24804896

I have found almost without exception ejector irons were case colored regardless of grade. I have fields, ideals and no. 0s that are ejector with hardened irons. I haven't seen an ejector iron blued that wasn't messed with.