My old Hove Foto Blue Book says the Werra 3 (or III) did not have a built-in meter; the Werra IV, V and Werramatic did. (Incidentally, yours looks to be what the Hove book calls a Werra IIIE, distinguished from the earlier plain Werra III by its rounded body style and striated black body covering.)
I'm pretty sure all those scales on the bottom relate to the EVS system, a somewhat irritating "simplification" scheme of the late '50s that combined equivalent aperture/shutter speed combinations into a single value. If you've got a meter that reads out in EV numbers, you can set any aperture/shutter combination that corresponds to the same EV number.
Most EVS systems didn't include a film-speed scale (the EV number just refers to an aperture/shutter speed combination, with no reference to film speed) so I'm guessing that Werra might have offered a clip-on accessory meter for your camera that would simply have read out an EV number assuming a particular film speed; the scale on the camera would have allowed conversion of this value for other speeds. And, as someone else said, doing it this way would have allowed parts sharing with the metered versions of the camera.