Bausch & Lomb introduced its Unicum two-blade shutter in 1897. On top it had a speed dial with speed scale from ½ to 1/100 sec. or 1 to 1/100 sec. plus B and T mode. It had two pistons, one to connect the tube of the release bulb, the other as part of the speed setting mechanics. For aperture setting it had a built-in iris diaphragm.
A stereo variant was available. It was one of the best shutters of its time.