I can not find any information about this instrument. It was in use at the Technical University in Eindhoven. It is in good working order. The construction is simple but delicate. There is a 6V light-bulb, a lens and a mirror. There is a small magnet mounted on a string inside a coil. On the magnet is a small mirror. When a current flows through the coil it generates a magnetic field. The magnet on the wire starts to turn and so is the mirror. The light from the bulb shines on the mirror and reflects to the transparent scale.
These meters are extreme delicate. The inner resistance is 173 ohm. The scale is 1 to 100%. On the scale there is a text that states 100%= …. uA. The number there is missing. The inputs are shorted by a piece of wire to protect the meter. It is very sensitive. If you move a small magnet above the wire you will see the meter move.
The lightbulb is mounted under the plate with the Philips logo.
There is no type or serial number in or on the case.
On this picture you see the light spot. The mechanism has no damping. It takes more as a minute before the spot stops moving. And if you move the cabinet a bit you can start all over. The screw on the top is connected to the wire and is used to zero the meter. Be careful not to break the wire. Often they are not round but flat and replacing them is very, very, very difficult. First to find the right wire and then the mechanical tension.