Chopin could have entered 
into [A] after Fontana had finished [FC]. In this case it seems slightly more likely than a possible oversight of the mark by the copyist or the engraver of FE, since a similar situation concerns also 
and 
in b. 267-268 (however, such serial oversights would happen both to Fontana and the engravers – cf., e.g. the ending of the Prelude in B
minor, Op. 28 No. 16 or the Prelude in E major, Op. 28 No. 19, b. 28-32). Anyways, there are no doubts as to the authenticity of this indication; as nothing indicates that Chopin would have wanted to forgo it, we give it in the main text.
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category imprint: Differences between sources
notation: Verbal indications