Magnet accessories are for science experimentation, magnetic properties, quality control. Certified iron filings, viewing tables and compasses for use with best in class Indigo ferrite bar magnets.
The Mark I magnaprobe uses ultra-low friction jewel mounts to give it exceptional sensitivity as low as 0.3 gauss. It can be used to detect very weak magnetic leakages or the effectiveness of magnetic shielding. Some people have even claimed to be able to measure magnetic declination!
The basic Mark II model is a must for high school physics or electronics classes who want to see the variation in magnetic field shape in the X-Y-Z planes. It is also a very handy tool for aligning magnets. The Magnaprobe's alnico bar magnet has N & S red-blue painted poles so you can use it to line up all your magnets so that their poles face the same way.
Magnaprobe™ is a trademark of Cochranes of Oxford, UK. If you see a similar black handled version selling for <$10, it is a cheap knockoff from "you know where". If you see a green or red handled version, it's a knockoff too, so Caveat emptor
Magnaprobes use gimbal mounted bar magnets find poles or detect magnetic flux with the Mark I ideal for testing magnet shield effectiveness.