In かちかち山, at least the version I am looking at, one of the opening lines is:
気のいい、じいさまとばあさまが、すんでおりましたそうな。
I can't figure out how to explain the bolded part. そう would either mean "seems like" or hearsay. Based on the conjugation of the preceding verb I conclude that we're dealing with hearsay here, which would fit the tone of a folk tale. But I'd then expect そうだ or そうです.
The only possible explanation I can come up with is that the だ is omitted, and then we're left with な as a sentence ending particle.