When tooling masters exist, but they must be modified, here is what we do:

First, we digitize the existing masters. We will use either our proprietary manual point digitizing system, or a Renishaw Cyclone system. The choice depends on the nature of the 3D surfaces of the master.

We will use our  software to convert the points into triangle mesh surfaces. This gives you several options:

We, or you, can take the files and produce exact duplicates of the original masters. This is useful for evaluation, and for making modifications without risking damage to the original masters.

We, or your designers can make changes or refinements to the new masters.