That's a lovely looking Ibberson 'sowbelly' stockman's Jake, the small crack in the ivory doesn't really detract too much..it's a wonderful all original knife. It looks to have carbon blades, most of the ones I've seen, I've owned quite a few, made in the mid 70s have had stainless ones..I think ?..(they were shiny anyway).
It's worth remembering the Ibberson knives that carry Stan's initials were assembled and made by him using parts mainly supplied by other workers at the firm. Stan's own knives that carry his own mark 'Stan Shaw' are made entirely by him.
Fairly recently I remember seeing the parts, liners, springs, blades, scales etc for three eleven piece ones on his work bench, prior assembly..a LOT of stuff..everything was individually marked each part made to fit exactly..Stan's a very skilled fellow.