Flywheel

I have another engine that has this type of dampner and it was also removed from a truck.

My 86 truck engine has a big bolt on its end that makes turning it easy.

I cannot see how this dampner/flywheel is held onto crank. How can I turn it easily? ( with a wrench ) I am imagining there is something behind this outer pulley I am just not seeing ?

EDIT: I said flywheel, I know its not a flywheel.

http://s675.photobucket.com/user/jhason2/media/Picture521_zps12a3fd81.jpg.html