Semantically speaking, they don�t have to be any particular thickness.  However, to be prototypic thickness they would need to be around 0.009� for 3/4� plate and 0.006� for 1/2� plate steel.  I have not measured them with a micrometer but they are most likely 0.010�, as they were probably etched from 0.020� so they are pretty close to 3/4� plate.  I have not painted them yet, but they look pretty good to my eye.

Regards

Bruce