Verifiability of what?  His letters are available and his work is widely distributed (in fact Science mentions as much) and they have been referred to extensively.  Keep in mind that this is not a debate on Oreskes work, but on Oreskes life.  Peiser's work on her essay, has had a profound impact - somebody looking to understand Oreskes' work and contributions would not have the benefit of a complete picture if we were to just ignore Peiser.  I agree - it's not an issue of fact, it's an issue of relevance.