I have in front of me a copy of the complete draft of the full score (HUL manuscript 0304). Kari Kilpeläinen suggests in his authoritative manuscript catalogue that this was planned as a fair copy, though Sibelius must have then changed his mind as there are numerous corrections and the music differs sometimes from the published edition.

Just for info, one place where there is no correction and Sibelius's handwriting is totally, unquestionably clear is at the beginning of the finale, where he lists the instruments alongside their respective parts: Stahlstäbe.