A seal (stamp) dating from 6200 BCE, roughly when most of Europe (except the Balcans) was still in the Epipaleolithic, and older than those from Mesopotamia as far as I can tell, has been unearthed at Yesilova Höyuk in West Turkey, in the Izmir metropolitan area.
The seal is shaped like a bull but the marking is a radial figure (8 radii, maybe representing the Sun or a star) and is speculated it belonged to an administrator of some sort.
The site of Yelisova Höyuk looks interesting because not much was known until recently of the Neolithic of West Turkey, the missing link between West Asian and Balcanic Neolithic. However the oldest dates for this site so far are whole millenium more recent than those from Thessaly, Greece, so this particular site does not look like going to inform directly about the ultimate origins of Balcanic, and hence European, Neolithic.
Source for the seal discovery story: Hürriyet - Daily News (found at Archaeology in Europe).
Much more detailed information on the site overall at the dig's site.