Occasionally I will ‘restore’ a NOS shaving brush - usually, I only do this when the original knot has dried up and it not serviceable. In this case, the factory installed knot was shedding profusely in the box - apparetntly, the glue had dried out. I opted to replace it with a very very nice synthetic knot and now we have a perfect blending of new and old in a NOS brush.
High Density 24 mm Synthetic Knot