It could mean you have the WS6 option. In most cases, if you have 15" wheels, drum rears, and the car year is 1985 or newer you most likly have the level II suspension not the level III(WS6). IIRC, the level II was called F41, which you probably have. But the RPO code is the only way to make sure...
One thing it definetly means, is that you have at least one step over base suspension ...
