As
compare
In As one can see that before the 2nd quaver of the lower R.H. voice a 
was initially entered. Chopin then changed it to a 
and probably added a cautionary one before the a
in the L.H. The accidental in the R.H. is also present in the version prepared for publication.
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category imprint: Corrections & alterations; Source & stylistic information
issues: Main-line changes
notation: Pitch