I think Caleb has it right that it is in fact Constanten and that it makes sense to accept the 11/6/68 date.
The fact that this tape isn't in the Vault suggests that it originates from a dub made for Constanten. The mix is variable and crude, like a mixdown to cassette done on the fly. If they were in the studio 11/5/68, the 6th would just be after midnight, and it would make sense if they started with the material ostensibly for the album -- Clementine -- and then later in the session moved on to rehearse material for performance. I just hunted up my original copy of the "Alembic" tape -- a TDK D-90 Normal Bias cassette that was among my first dozen tapes, acquired in '82. It is labeled "Alembic Studios 11/6/68", doesn't include all the Eleven material, and has the Rio Nido 9/3/67 Midnight Hour for filler. It is probably early in the tape's cassette circulation and fairly low gen but the signal is considerably degraded compared to the digital copy. Pigpen got his B-3 back before long. He kept contributing keyboards alongside T.C. and later alongside Keith. At my first show -- Winterland 10/25/69 -- the Dead's stage set-up was remarkable for the two drum-sets flanked by two keyboards, one probably a Hammond. --
