NSDAP flag: information/authentification pls

[scf]

Hi-- I am new here. This flag has come into my possession. It came into the possession of a relative no later than the very early 1990s, and likely in the late 1980s — possibly through a friend, or possibly purchased at a show or auction. I'd love to get some opinions as to authenticity, as well as the specific purpose/use/possible provenance of the flag. I can post better photos and details if necessary. It roughly measures 94cm x 94 cm or thereabouts. Many thanks