Other
Perhaps more of an oddity but, as concert promoters/agents/venue managers clear out their hardcopy/paper files over time, occasionally old tour riders/venue contracts (and associated correspondence) may surface. I've only seen unsigned versions to date but sometimes these are in original/letterhead format, sometimes they are copies or via fax/telex - likely all dependent on the source of the material.
Riders/correspondence for the 1990 Holland shows.
Riders/correspondence for the 1993 European Tour Part I.