Interesting. It's definitely a smaller brake than the usual Arai for tandems, maybe it is intended for a utility bike or something.

On the more common Arai brake, the brake drum and shoes just sit together, they are held together once they are assembled with the axle and everything.

Does the inside of the brake drum have threading to attach it to a hub?

It probably would be fine on minor hills, but I'm not sure you could count on it for any significant descents.