Acid Free Paper

I notice in some editions it is expressly stated that the edition is printed on acid free paper but it seems earlier editions are not so explicit. I know Easton has always used "quality" paper but have they always used acid free paper? If not, is there any info about what year they went exclusively acid free? Has anyone noticed discoloration or foxing on older editions?

It seems likely that they have. Without digging around for my oldest EP prints, I’d guess that the inclusion of acid free paper in their advertising began very early on, perhaps in the 70’s.