Mercury II
Universal Camera Co, Mercury II. 1945-52. Half frame, rotary shutter (hence the semi-circle on top). The far left numbered dial is the frame counter, the knob sticking out over it advances the film and winds the spring. The next knob right is the shutter speed. The top right knob is the film rewind, the rewind knob front bottom releases the sprocket mechanism. Focus by "best guess" on gauge. When the shutter fires, the shutter speed knob rotates 360 which is fun. The internal shutter is two half discs that open and close to make a wide or narrower slit. The shutter rotation speed is constant, but the slit size dictates exposure speed. A very fast camera in its day (1/1000th)