Those are weights for lofting rails (I am not sure that is the exact right term, my memory isn't what it used to be) Basically, the rail and weight set made up a very long flexible french curve. They were primarily in the aircraft and boat building industries to allow full scale layouts of wing airfoil and boat hull profiles. These layouts were drawn on large sheets of velum laid on the floor of the design area. The flexible rails have a groove in their top edge and the points on the end of the weights insert into that groove to shape and hold the correct curvature of the rail. In pictures I have seen, there could be as many as 20 to 50 of these weights along the length of a rail.