This might be a "one key" system, which doesn't use a crank puller tool, because the removal "tool" is built in. These were popular for a while.

In this design, the bolt is kept in the arm via the "dust cap" ring. When you back off the bolt far enough, it pushes against the ringpushing the crank arm off the spindle. You're top-off is if when you turn the bolt, it loosens and is free for a turn or two, then jams. That's it jamming against the ring, continue turning it to the left and you'll remove the crank. Note that a decent amount of torque is needed. Also before starting, spray some oil into the gap between the bolt and ring, to eliminate the dry friction when the bolt is backed up into it.