If you mean the grey bit, it's old cut putty, from the failed approach graft I tried. Parts of the rough bark around there are peeling though and it's smooth underneath which is making it look like it has reverse taper (well worse than it had already anyway).
Thoughts about it's path to get to now... well just that I stuffed a perfectly good stock tree from the start, but it's finally starting to be an ok tree (in my eyes anyway). Also I will never neaten a trunk chop like that again... This is has been a hardy tree on which to experiment techniques on.
