Early Style 4 Chime Alarms have the time key close to the time set knob, and the time key has male threads. Standard ones have wide spacing from the time set knob to the time key, and the time key has female threads.
Time Set Knob to Time Key Spacing Narrow:
Early Style 4 Chime Alarms have the time key close to the time set knob, and the time key has male threads. Used from the beginning of Style 4 Chime alarm to ca. late 1934.
Time Set Knob to Time Key Spacing Wide:
Standard ones have wide spacing from the time set knob to the time key, and the time key has female threads. The wide spacing is achieved by the time barrel bridge having two extra winding gears. Used from ca. early 1935 to the end of Style 4 Chime Alarm production.
