It would think that it would take nothing more than the Diana coming on to the market. Some industrious sole in the UK liked it and saw the possibility of using it as a model to make a copy. Pressed steel was such a common manufacturing technique back then it wouldn't be difficult to commission or make a production set of tools. Which is exactly what the original inventor of the Sharpshooter did: all DIY tooling.

I remember that Haviland and Gunn sale, too. I had one in better condition that I sold for $1500 and the guy who bought it from me thought I had ripped him off. Wanted to call him and point out the silly price but he's still wouldn't talk to me.

NB: I am of the opinion that the "original" Girandoni's floating around these days are not original at all. They are instead the English copy of the Girandoni. The best evidence we have indicates that the military model was 13 mm. All of the ones seen today are 11mm and, IMO, very English. The simple fact is that there are Staudenmayer and Mortimer examples of this same 11mm gun that has the (bogus) G and serial numbers on them. Of course, that doesn't make the owner's of these guns very happy with me, but, there just isn't much I can do about that.