Regardless of what a bike originally came with, I have found a couple of oddballs out there. There is no substitute for proper measurement with a digital caliper.
I had a late 1980s bike with a 26.2 crown once. That was a PITA.
Tange Passage comes in both 27.0 and 26.4 sizes.
http://www.amazon.com/Passage-Thread.../dp/B004JKGS1W
http://www.amazon.com/Tange-Passage-...394874-9907223