To be honest, I do not believe there is such a thing as a "handwriting expert".
Handwriting varies incredibly, even in an individual.
Most of my signatures these days look like I'm faking them.
No two are ever the same.
What needs to be analysed are the tiny variations in the pressures exerted while writing and the time-related fluency of execution, not the shapes of individual letters. That is more akin to phrenology (bumps on the head relate to personality) or physiognomy (if you look evil outside, you are evil inside).
I don't know how any of that
could be analysed while engraving.