Studio One, EMI Studios, London
A rough mono mix of "We Can Work It Out", made between 5:00 and 5:30 pm, not for record release but for the Beatles to mime to during the video-taping of The Music Of Lennon & McCartney.
It was only when they heard a playback of this mix-for-TV that the Beatles realized the song's vocal tracks required an overhaul. They were overdubbed again the next day, October 29th, instantly rendering this mix unusable.
Source: The Complete Beatles Chronicles - Mark Lewisohn