cabin in the sky 1942 acetate

this past weekends i found a white Metro-Goldwyn-Mayer-Pictures acetate of Ethel Waters performing "Happiness Is a Thing Called Joe" from Cabin In The Sky" this is a white label . the audio has a count off at the start of both sides " 1-2-3" then a slate being hit, then the music starts with Mz. Waters singing, there's a date on it 9/9/42, on the cd re-issue that Rhino put out, this song was arranged and orchestrated by George Bassman, and recorded 9/4/42, five days before the acetate. whis song was written by Harold Arlen & Yip Harburg, and was nominated for an Academy Award for 1943. my question is, what is this? could it have been used for the playback in the film when Ethel Waters lip synched to the track during the filming of the song? would it have been given to the song writers/ director or others? if so, why was the slate recorded, i know they didn't record these live on the sound stage.. the labels aslo say "cued" on one side, and "no cue" on the flip, both songs on the record, one sounds like it has a little different trail out chorus, any thought would be apprieated, i also have this as an MP3 if anyone would like to hear it

bhblackburn, March 30, 2006; 1:11 AM