Hi all, regarding the mentioned leather rolling machine.
This is a machine used by shoemakers. Traditionally the veg tan leather for the insoles(not a slip-in insole, but the actual foundation of the shoe, as the uppers were sewn to this insole) and the outsoles were soaked in water, then wrapped in cloth/paper allowing the moisture to penetrate the leather but absorbing all excess. Once the leather was damp but not soggy, maybe next day, the pieces of leather would be hammered on a stone slab, starting from the centre and working your way to the edges. Hence the wide face of the shoe hammer. This would compress but more importantly pre stretch the fibres. While still damp, the insole would be nailed to the last, a few nails in the middle and nails all around the edge of the last. Now the leather was allowed to dry, the outer ring of nails preventing the insole from shrinking together again. This process was important to prevent premature stretching out of shape of the shoe once the shoe was worn. The same was done with the outsole, except this time it was sewn to the welt while the leather was still damp. The above leather mangle is doing that job. The bottom concave brass roller turns faster than the convex steel roller at top. There is pressure on the leather and a certain amount of drag, which helps to stretch the leather. A 6 mm outsole has quite a bit of resistance. Yes, the rollers should be smooth.