The steel is a bit of old leaf spring, which was quite rust pitted, which is why the tool has not got a very highly polished finish. It is hardened and tempered to a purple colour (towards the tougher rather than harder end of the tempering spectrum).
The spring clip is a bit of hard stainless wire, 1mm diameter, which I think was a filler rod for a TIG welder. The clip spring tension is a little weak, I was working by trial and error, so I might alter it (I would just about have room for a clip made of 1.6mm rod, but I don't have any stainless in that diameter)
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