This version is known through Bach's pupil's copies, such as J. P. Kellner's P 804 (dated 1726) and J. C. Vogler's P 1089 (dated 1729).
It is written in 2/2 (¢) metre and 34 bars long, lacking the 3rd
exposition (bb.68-83 of the later versions) ;
Vogler's version (with many more ornaments and fingerings) is also worth studying, for it is highly likely that they were most likely written in under Bach's supervision .
Based on the early version, Bach changed the notation to 2/4 metre (increasing the number of strong beats) and extended the piece (bb.68-83) on the 'London autograph' where two layers of reading can be reconstructed. Ornaments are not fully written in here .