In the Channel 4 documentary on How To Build British (Morgan episode), about 45 mins in there is a sequence showing the louvres being stamped. There is a line scribed on the tool and a matching line on the underside of the bonnet (looks like it was done with a chinagraph pencil, but probably an engineer's fine marker). I'm not saying I could do it, but also not quite eyeballing.
[img]https://www.tm-img.com/image/38YWU[/img]
[/img]https://www.tm-img.com/image/38cZs[/img]
[img]https://www.tm-img.com/image/38gc1[/img]
[img]https://www.tm-img.com/image/38ksj[/img]












Peter
2009 3-litre Roadster "Ivor", royal ivory / green