Could be hiding, protection, or sound absorption…obviously stated. When I put a rust-free box on my Dakota, I undercoated it as all it had was primer and original paint overspray on cherry metal – for protection. Over the years learned a bunch looking at restored vehicles. There’s grade A, B, C, and so on quality restorations. Some have taken tons of photos of their restoration. Have over 250 photos of my ride, anyone who I might sell it to someday will see it naked about every inch of it inside, under, and during its phases of disassembly and reassembly. Phone cameras are handy, unlike doing my first resto before phones with cameras. MO, want to be pretty good spotting hard to see imperfections or shortcut work; learned a lot from versed body people. I’ve seen rides so nicely restored and much better when they have a photo shoot of what was done. There are those places bent on max profit flipping cars using the lipstick on a pig approach. If one doesn’t have the knowledge, locate someone who does before buying.
