I recently got a firesteel on BCUK from Mozzy, who goes by the username Lord Farquhar on a number of bushie/knife forums..here's a few pics and a quick trial of the steel
as you can see it's a big steel and I have largish hands taking a size 9/10 in gloves so this is a biggish lump of metal easily taking all four fingers
and in hand, as I say, quite large and feels a little unwieldy because of the size, an inch or so smaller may have fitted a three finger grip more easily
and how does it spark? Well quite decently, not as ferocious as some I have in my collection but it throws decent enough sparks to light char cloth and as you can see here, some amadou.
It was made of water quenched O1 steel and does a decent enough job.
I know Mozzy usually makes Knife blades (I have a few myself) and this maybe a departure for him, but it works well and I'm sure we'll see a few more from his stable soon.