Issues : 4/4 or 2/2

b. 1

composition: Op. 29, Impromptu in A♭ major

 
 
..

The  time signature is most probably an error or FE's and GE's revision. Changes of time signature indication of that kind are to be found on a number of occasions also in other Chopin's pieces issued by those publishing houses – cf. e.g. Etude in C, Op. 10 No. 1, bar 1..

category imprint: Differences between sources

issues: Changes of metre , Inaccuracies in GE , Inaccuracies in FE , 4/4 or 2/2