As before it seems to me too that if the game is just to source some holdfasts then it's probably most cost effective to buy from the US.
If on the other hand it's about hand made then by all means have a go. I've several of the GM variety.
To waffle a bit. My sense (purely from the feel and the 'ring') is that whatever the steel is it's a bit more lively/springy than annealed mild steel: i.e. something with a little more carbon and/or some alloying elements - or else it's work hardened from the drawing and/or bending processes. This'd make some sense, as if it's too ductile/fully annealed/dead it'd probably deform far too easily when you whack it, and might lose it's set.
They have a matt but fairly bright finish, could be it's drawn stock of some sort (this too would work harden it a bit), maybe a higher grade reinforcing bar or something like that.
The Popular woodworking article mentioned before has quite a bit in it (but never really bottomed) what the magic ingredient in a reliably functioning holdfast is. Did they conclude that the angle between the clamping foot's face and the shank was important? There was suspiciously little mention of the metallurgy or heat treatment/state of the steel. Either way it'd be maybe be worth getting a copy to the blacksmith. (I may have it somewhere if it would help Wiz)
Here's more heresy. It seems to me that the blacksmiths bit is perhaps mostly in forging the foot, and that there's probably quite a grey area between 'factory' and 'hand' made.
There's lots of CNC bar and tube benders about these days that would probably give a very accurately reproducible bend, and not cost a lot. Maybe mix the two? I can't imagine a guy whacking a bar around the tail of an anvil getting it spot on every time....
Heat treatment is probably the other variable. Quenching and tempering by a blacksmith is possibly a bit hit and miss too unless he's using ovens and the like. On the other hand some sort of drawn bar might be sufficiently (and consistently) work hardened as it comes, and the bending would add to this.
I wouldn't worry to much about the patent, as there's a gazillion ways to form them unless there's something very subtle going on in there. The point is that they are handing patents out for almost anything these days.
If you really want it to look hand made and old you could chuck it in one of those fettling drums full of steel slag or the like for a while - it'd roughen up the shank nicely too :wink: