It's 5'x8' two-sided. .063" aluminum faces flush bonded somehow to a 2" frame which runs the perimeter of the sign. I see no rivets; the face of the sign is completely smooth. The face is divided into two tenant panels which are only delineated by being on separate pieces of printed vinyl.How big is the damaged face? If a new panel is out of the question maybe cladding it with a thin, wrapped aluminum overlay of the entire damaged panel. Can't tell from the photo what the framing looks like so might not be an option. Fixing the dent will put any future issues or failures on you, instead of the company that made and shipped it.
It is the manufacturer who is asking me and will pay for whatever repairs are made.
Obviously they are trying to avoid having to make and ship another sign, which would really be the ideal solution.
If they were willing to let me know how they made the sign, i.e. how the face is bonded to the frame, a second best would be for me to make a new aluminum face and put it on the frame. If we did that, I'd have a local auto body shop paint it to match the brown, and have the original manufacturer ship me the vinyl panels with the printing on them.