Surfing online I discovered some MB2 with different bridges (see photos).
Which one is the newest? Which one they use now?
One is for the fretted version and the other one for the fretless one or they just changed the type of bridge over the years.
I think this is the right info: The one on the left is the standard bridge. The one of the right is a custom that allows for intonation changes (it is based somewhat on the Solid 4). I think Rob did that for some small scale fretted instruments, but I've had fretted basses with the standard bridge. I've never seen the moveable bridge on a fretless.