This review has been awarded.
I think you are definitely going in the right direction in terms of classic simplicity. Looking through your previous iterations, though, I think the image in concept #4 from v1 is much stronger. The current one would be harder to scale well since the abbreviation would get lost. If you want to go with a chemistry-like theme, though - just take out the circle and increase the abbreviation and it will look like an element from the periodic table!
In terms of type, I like the this iteration one much better - it is clean, uniform, and easy to read. Placing it on one line and centered with the box (somewhat like interation #2) would work as well.