Gareth -
My motor is also open on the back, so I'm assuming this is just the design. Maybe the thinking is that it would be attached to the Bolex anyway, so there's not much risk there.
I think I can provide a little clarification on the drive key (I think that's what the plastic connection to the 1:1 shaft is called): As you probably noticed, it's possible to remove the drive key by loosening the little screw on the side. I have both a drive key that fits a RX5 (and I'm assuming an SBM as well) and another one that fits an RX4 (same as what yours looks like). It would be nice if these were metal, but I kind of wonder if the thinking was that if something went wrong, it would be better for this easily-replaceable part to break than for the drive shaft in the camera to break.
I sent an email to Procam, the U.S. dealer of Bolex cameras and the place I use for repair (I'm at a university and we still have around 20 Bolexes that get used every semester). I'll let you know what I hear. If I don't get any info there, there's one other resource I'd try, too.
I'm not sure what to say about powering the controller. The SCC-300 is powered through the motor power, so there's no other connection other than the 4 pin from the motor. The red mark is usually positive, but not 100% of the time, so that might be worth more research. If you need to find a connector to fit your controller, you may be able to figure out what it is by measuring and cross-referencing with Lemo's web site: http://www.lemo.com/en/standard-range/b-connector-0?domain=[term_node_tid_1]
If I had to guess, I'd say this is a Lemo B connector. I forget how the sizes are marked.
Mouser is a useful resource here as well: http://www.mouser.com
- Bruce