There is a really great guide about all of the stamps variations. Probably a lot more to it than most people realize:
www.elitefourum.com/t/1st-edition-stamp-variations-lets-iron-it-out/17624/1
There is actually:
- Thick 2D Stamp
- Thick 3D Stamp
- Thin 2D Stamp
- Thin 3D Stamp
- Thick Grey Stamp
- Thin Grey Stamp