it's very similar to a Mustang bridge, but is wider to allow proper intonation of the low strings on a Bass VI style guitar. A French luthier makes them. Quite a hard piece of gear to track down, especially with Bass VI Parts being so rare.
I'm still saving for the neck, so I'm afraid I haven't got it all assembled. Too many builds going on, and I just tore my ACL so need an expensive operation now..D'Oh!
I should also point out that the pickups are sitting on some foam because they actually sat too low in the pickup cavities, i thought. Though that will be easier to tell when it's all put together.