Magnaprobe MK I,- 3 Dimensional, Precision. 

The Magnaprobe TM magnetic field indicator is a small magnet suspended in a gimbal mounting. 

It can be used to show the three dimensional nature of the following:
* Forces between magnetic poles 
* Induced magnetism 
* The shapes of magnetic fields between like and unlike poles 
* Direction of a magnetic field around a bar magnet, a wire or a coil 
* Properties of a field produced by an electric current. 

The Mark I is more sensitive than the Mark II, being mounted on precision bearings and balanced to show the dip of the Earth's magnetic field.