The crankshaft is a large turnbuckle that allows for throat adjustments. The slider adjustment at the top of the crankshaft maybe for minor adjustments but I'm not sure. If I swing it furthest back it causes erratic hammering.
Those two odd elements at the pivot point of the hammer arms that essentially look like two Big Macs - three metal buns sandwiching two 133 year old rubber patties. I think they act as shock absorbers. I'll have to source those parts sooner than later.