[unknown] (special purpose label - DO NOT USE!)

This is a special purpose label.

Do not use this as a label!

• If the release has no branded production or distribution label (a.k.a. imprint, logo, trademark), use [no label].
• If you're unsure about which one of the branded labels to use,
  • leave the label field blank
  • upload (via Cover Art Archive) or link to (via edit note) scans of the exact release in hand so that more experienced editors will be able to finish the job for you.

Why keep this label if it's of no use, then?

Because in the past people used it for all sorts of purposes, and that stuff needs to be sorted out, not just blanked.
But mostly because people will eventually recreate this label anyway, so keeping the entry at least helps us steer it.