“A Sarm Studios 10" Reel To Reel tape from 1975 features an unpolished version of Sweet Lady. The track is the same mix and performance as the album version, except that the ending does not fade cleanly. Instead, it is the band continuing to play the backing track until a sudden stop.“ Queen Vault (for if you don’t know about this)
It's unpolished, but it's the same mix? Doesn't sound unpolished - "just" the album mix before it was faded out during album compiling/mastering. Also, no such thing as a 10" reel. 1/4" seems more realistic - 2" at most. You measure a reel by it's width, not from the middle to the outside.
I think the description on Queen Vault is all you need to know. It's the same as the album version, just without the fade out, so it's a few seconds longer.
I believe it is a 1/4" reel to reel tape, not an acetate.