Wow, this is a quandry then? On the CR List?! I feel I've accomplished something at last to get the collective head a scratching.
Braze-ons seem to come and go for no apparent reason. The frame in question has lots of them (gear lever bosses, bare wire brake cable stops, cable eyes, pump peg and those pesky bottle cage bosses.) And this on a supposed c. 1965 frame. But gear lever bosses and the bare wire arrangement seems to have common in the 1950s into the mid 60s and then less so? Why? Most late 60s-mid 70s machines have brake cable top tube clamps. And clamp on lever bosses. I don't think the gear lever bosses are a later addition since there is also no "pip" on the underside of the down tube to line up a gear lever bolt-on fitting.
Anyway, I've taken some photos of this mystery Quinn frame and posted to my Wool Jersey site:
http://www.wooljersey.com/gallery/Peter-Kohler-Cycle-Collection/Harry+Quiin/Peter KohlerWashington DC USA