It must be Clemente PDaa (Hairline) free font by Alan Prescott (Prescott Design, 2003)

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I found it using "Find my Font": http://www.findmyfont.com

Does the "s" in Clemente remind you of anything?
It's a difficult letter to make...

hhp

You are right, 's' looks exactly like Helvetica-Thin ...

The very delicate modulation between the bowl and stem of the "a" was the initial clue. Very few people who implement such sophisticated details give their stuff away... Sadly though others often steal their stuff and give it away. Let's not help that along.

hhp

Go check the spacing of Clementine’s lowercase ‘j’ …