Looks like a limited production unit. I remember seeing these.
Very nice construction inside.
Good capacitors.
Switch for roll off.
The sliders all you to attenuate a bit more, if you were using a device that clips on input.
Most modern flash recorders have a wide range of input levels, but this is certainly nice to see. You can set the levels of the sliders inside to box, tape them down and not worry about it.