OP was asking about parts, not every ones opinion on safety. Maybe he just wants to hang it in the rafters. I've saved my Dad's old wood extension ladder and plan to display it with the rest of my old stuff.
Manioso is correct, 4 ton Weaver. The 4 ton front wheels are below the saddle and the 10 ton wheels are way taller than the saddle. You're missing the top cover with the spec. on it. I haven't seen a triangle saddle on one until yours.
We call it rack rust around here. it's hard it keep it from not rusting with all the moisture in the air. Yes on the removing it before welding and painting.
:) Thanks, it's hard to pass up the unwanted boxes that people are getting rid of. There were a lot of those Craftsmen boxes sold. What really freaks me out is I manage to fill them.