Before the internet opened the doors to the world, we thought they were rare like many other now collectible things.
Markings as you describe are not the norm but not uncommon.
I've had dozens of sets with only A and B specs written on the limb.
Seen often in dimpled sets and i have found them marked that way with limbs of high weight mostly.
They have no higher dollar value either in my experience.
Hope I helped.
.........Philip