Interesting, if a little sketchy. :^) He needs to scan that map and lock up the original, with a cover letter describing the whole process. He may have to get some help with this search, maybe from the French gubmint.
I’ve gotten a few calls when it comes to treasure hunters. Most of them will just offer you a cut of the treasure. This guy said he would pay for all of my expenses up front.
I don’t think he was scamming me - and I forget the details of the story but it sounded reasonable that the treasure might still be there.
And he knew which castle it was, and the map lined up with existing features. So it limited the search area. Not like trying to find Pancho Villa’s stash of gold and weapons that was buried in some valley that is 20 miles long.