I restore a lot of oldies and see this very often in unrestored ones. I feel it has to do with honing strokes and was done by old Honemeisters for future reference when the razor comes back for a refresher. No one has been able to crack the code so far. I am restoring an old Johnathan Crookes and see it once again in the ivory.
As one can see, 90/4, 7/12 and lastly (obviously crossed off) is 64/2. These fractions are always top-heavy and I have seen them on a wide variety of razors and scale materials. I would be angry to see it applied to mine by someone paid to do work, but must have been acceptable practice back in the day!

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