A copy of this large sharpening stone which shown to me eleven years ago by the former managing director, who was the first to explain to me of the concept of the wheel-shaped stone. According to that suave fellow, following the hollow grind procedure, TI sets up their cutting edge on a pair of wheels seen here (which have a significantly shorter effective diameter than that which follows), and then they move on to this natural Pyrenees stone for a bit, which (- again, ~12yrs-old info, but highly unlikely to change) they shape by hand to be slightly convex (and too subtle for you to see in that video, but I assure you a ruler placed on the stone in-person would see it), and finishing via a strop regimen as here. Their idea is that by thinning the bevel form and only leaving a small piece, the work with the bench stone (either flat or very long diameter) only has a tiny patch of metal upon which it can work, and then refining it with the slightly concave surface of a pasted strop ensures they are polishing at the very apex of the bevel form.
I don’t know their particular numbers of effective diameters they use to impart their preference toward the razors’ bevel forms. But as this is a coarser natural stone appropriate for bevel-setting a straight razor or finishing a kitchen knife, in my professional opinion for the use with straight razors it would benefit from a reduction of thickness of at ~2mm over this stone’s ~12″ length, no easy task shaping by hand as they do. You can use our dedicated plate, as I myself certainly will do with one piece of this inventory once we get them, but as this stone exceeds the length of most sandpaper and our plate’s 11″ span, you’ll have to work in phases, and in the end you can certainly get an effective and consistent curve but not easily one as short a diameter as the plate. I’ll have to put hand on stone to see just how difficult it is to shape this before I’d offer a pre-shaped one for you as an end user. Personally for my own work, I intend to shape one side convex, and use a granite surface plate backing sandpaper to truly flatten the other side.
FWIW, I was told 12yrs ago by their old director that they used this stone with new, clean low weight motor oil. He did/does have a thick French accent, so perhaps something lost in translation, but as I’ve no intention of ever reselling my piece of this once I get its surfaces prepared geometrically to my own standards, motor oil I shall use.