This is Western Electrics first dial telephone. The 50 series was produced between the early 20’s to 30’s. Early microphone only worked at specific angles, so the microphone is secured on a phone itself. What results is the classic two piece design. These phones originally used type 2 dials, which make the characteristic clickety-clackety sound.
To operate these candlestick telephones work, one needed a separate subset box. The subset contained the ringer bells and other necessary electronics. Wiring a telephone without a subset box can permanently damage the telephone.