I have one of the reed pullers that that PPCo sold.  It appears to
have been made from #36 piano wire (0.090") that had a sharp bed at
the business end and had most of the outside of short leg ground off
to leave a sharp hook.  I am not sure but it may have had the hook heat
treated for extra strength.

I have used it for years and I have never damaged the hook and some
times I have had to pry on the handle with a screw driver to break
loose a really tight and corroded reed.

John Dewey