You may want to consider sending the lens to S.K.Grimes and have a new scale made.

   You can calibrate the aperture scale for the new lens. I
would make a new scale, perhaps the simplest method is to
put some white tape over the old scale.
   The _effective_ aperture of a lens is not the size of
the hole in the iris diaphragm. Rather it is the diameter of
the entrance pupil. It turns out that this is easier to
measure than the physical diaphragm size.
   You will need a card with a small hole in it. A
flashlight or other small light source. A flat mirror large
enough to cover the front of the lens. Some thin paper.
   The lens and card must be mounted parallel. If you are
working with a view camera you can use the camera as a
makeshift optical bench.
   Mount the mirror over the lens. Put the flashlight in
back of the hole in the card. Adjust the lens until the
reflected image of the light is focused back onto the card
near the hole. Now, remove the mirror and place a
translucent screen over the lens. Thin writing paper works
fine. There will be a circle of light projected onto the
paper. The diameter of this circle is the _effective_ size
of the stop. It may be larger or smaller than the physical
stop, depending on the magnification of the lenses in front
of it.
  The diameter of this circle of light is devided into the
focal length of the lens to get the stops. Simply adjust the
iris to the sizes you want to have marked and mark them.
This is a very accurate method of calibration.
  I am presuming you know the focal length of the lens. The
marked focal length will be close enough although you can
use the same rig to measure the actual focal length. I've
posted the method to this group several times. Probably a
Google search for my name and the keyword autocollimation or
autocollimate will find them.