2843. Thornton-Pickard Manufacturing Co., Pickard, G. A., and Woodhead, C. G. Feb. 9. Shutters.-Relates to a stop for holding open shutters such as described in Specification No. 24,319, A.D. 1899, for the purpose of focussing. Figs. 2 and 3 show the stop in two positions. The shutter leaves A are traversed by the levers B, C, one of which is actuated by the lever d and the spring D. On the lever B is a projection E, which is arrested, with the shutter open, by the stop G, when. it is in the position shown in Fig. 3. In the position shown in Fig. 2, the projection E is free to move without coming in contact with the stop G. The stop is fixed on a slide which is actuated by an external knob H.