One of the designers I follow on twitter posted this a while ago, can't remember who or I would ask them. I believe it is a mockup for Royal Mail slip that they leave when they "deliver" your parcel but you were out.
It looks similar to Archer and ITC American Typewriter, but it's neither of those.
Any help would be greatly appreciated,
Thanks in advance.
The full image can be seen her http://cl.ly/1Aj2