[TARNATION !!!]

Had a look at two dismantled VH's. The left side screws bearing the "-" mark include:
Cocking Crank Pin Stop Screw
Hammer Screw
Hammer fastening screw
Floor Plate screw (front)

The corresponding right side screws are not marked.

Both have the longer rear floor plate screw, so there is no need for a "+" mark. I have had three apart and have not seen a "+" mark on any of them. All have had the longer rear floor plate screw.

Cheers,
Jack