This old-fashioned kitchen gadget is a hand-crank rotary egg beater, also known as a manual mixer.
The two metal beaters were placed inside a bowl while the small side handle was turned. Its gears made the beaters spin quickly, allowing cooks to beat eggs, whip cream, and mix light batters without electricity.
Tools like this were common in kitchens before electric hand mixers became widespread.
The correct answer is a vintage hand-crank egg beater.


