Jens, are you out there!!
Jens has accomplished some of the most definitive research on the katar, along with Brian Isaac, as well as some of the best discussions concerning Indian metallurgy, so I hope they will come in on this.
Delor,
Welcome!!
I very much admire your straightforwardness and the responsible approach you are taking toward producing an example of the katar. It is extemely encouraging to see a craftsman working to preserve the magnificent metalworking skills that existed in India when these weapons were made.
I would suggest, if possible as I know you are in France, to contact a publication here in the U.S. titled "Blade" magazine. It seems there have been numerous articles on authentic forging of such blades, but I am uncertain of issues etc. I will add anything further I can find.
All best wishes and success on your project,
Jim