Thank you polymath for all that info.
I have seen your detailed instructions using bullet casings, very impressive too with the level of detail, tools used and suppliers etc.
I have managed to get Roger Patterson's book and you are indeed, mentioned in the book discussing the use of casings along with a photo.
The chap in question, regarding the punch which started this thread, mentions in the comments on youtube that he may produce a video on the making of it. I was hoping to make contact to discuss his future plans, if there are any.