From left to right: U610A grey OB, U611B OB, U611B N.N., U611B N.N. The first two pieces are wet process Ohio Brass, embossed logo on ear. The last two are dry process Akron products. Interestingly, only the brown OB made use of the teats as a firing rest. The Akrons and the grey OB are all petticoat rests.