Fw190 main tags are represented by several 4-sided and 6-sided styles; some examples may be found here (thank you Andrew):
http://fw190.hobbyvista.com/plates.htm
There was considerable variation in the information on the plates - both as made (i.e., nomenclature etched on manufactured blank plates) and as used (i.e., aircraft-specific entries stamped in during production).
The plates were riveted to the exterior of the fuselage on the left side in the vicinity of the Balkenkreuz. A careful look at period photos will reveal the plates when not painted over (as often was the case).