It's another bootleg version of the 'Out from the Dark' LP.
Some tracks are great versions with Dead on vocals, the version of 'Freezing Moon' is definitely worth hearing if you're Mayhem fan. It has far more passion than the well known studio version with Dead although the sound quality is worse on the rehearsal. On other tracks the vocals are far from perfect and it seems like he's still figuring a way to make them fit the music better, 'Buried By Time And Dust' is a good example of this. But if you compare 'Buried' with the version that's on 'De Mysteriis Dom Sathanas' you'll hear how it didn't take much alteration from Attila to make them fit the track perfectly.
I'd stick with the 'Out from the Dark' LP, it has way better sound quality and isn't extremely rare. 1800 copies exist of it (minus the damaged ones) so there's a chance of finding it somewhere.