Lens Aperture Motor - wiring
There are a couple of resources on the net about identification of stepper wiring. The most common are 4 and 6 wires (6 wire being the almost universal wiring).
There is another kind of actuator you are likely to see in a camera, a voice coil: put a current and something moves depending on how much current you give (microamps, usually). It's actually one of the fastest electric actuator around (hard disk heads and laser scanners are done in this way). Your shutter seems to work this way, try putting an intermediate amount of current to see if it goes halfway