No, it’s a magnetiser used to activate the magnetic field in all of the speakers’ magnets. When drive units are built the magnets are supplied un-magnetised for ease of assembly (if you’ve ever tried to align a speaker’s motor unit around a magnetised magnet you’ll know it’s damn near impossible!)
Once the drive unit is built, the last step is to sit it into this unit, and press the button which discharges a large electrical charge from some hefty capacitors into a coil around the magnet. This lines the particles in the material up properly and establishes the magnetic field.
As has been mentioned, if you get it wrong, it can be a bit dangerous....