This is a ZC25-3A insulation resistance tester (megohmmeter) used for measuring electrical insulation resistance.
It features a hand-crank generator to produce the necessary test voltage, typically around 500V for this model.
The device includes an analog pointer gauge to display resistance readings in megaohms (\(M\Omega\)).
It is enclosed in a protective plastic or metal housing for portability and durability in testing environments.