If its camo appearance, its 36. Otherwise, probably during the fight between ZAFT, EAf and Logos which is about 38 or 39. I think...

Regarding Neo, I came across a very interesting theory regarding Neo, Rey and Dullindal. The site is http://seedgenesis.net/index.php?action=theory10.

For theories regarding Dullindal and Logos, i direct you to http://blog.rodtv.com/index.php?cat=28

Personally, I'm intrigued by their theories but they do sound quite logical.