I wonder if even Dunlop knows! Seriously, the squash ball manufcaturing process remains a mystery since the game was first invented. So many types of balls come and go, and no two have the same bounce! ( not the fault of the ball as court conditions make a difference too).

Faraz
http://SquashClub.org

http://www.squashplayer.co.uk/squash_balls.htm
sections on history of balls, how they're made,
tested, etc.
A project? Hmmm, an attempt to make copy of
the Dunlop Pro XX from the orient perhaps?