Here is a comparison of the 3
basic Black Scribble versions:
1) F-Scribble - first letter F clearly visible
2) Loop-Scribble - first letter F is altered. Created a partial F or 'loop' pattern.
3) No-F Scribble - first letter F is airbrushed away.
4) Version found in 2013 by bnorth (hi Ben).
The first 3 are considered 'basic'. Most common black scribble versions found. If I was the rank them - they would be in the order shown (easiest to hardest). The 4th card is currently a unique variety. Other black scribbles would be the 'semi-airbrushed' version or 'Circle Scribble'. Very rare.