Today in 1972, US Patent 3693828 A was issued, an invention of Raymond H. P. Kneusel and Vinson S. Potts, assigned to Crown Cork & Seal Co., for their “Seamless Steel Containers.” Here’s the Abstract:

A steel beverage or beer can of the seamless type having a unitary body including seamless side walls and an integral bottom with an end double seamed to the top of the side walls. The bottom comprises an outer frustoconical surface extending downwardly and inwardly from the side walls, an annular bead for supporting the can, an inner frustoconical surface extending upwardly and inwardly from the annular supporting bead, and a recessed domed central panel extending inwardly and upwardly along the axis of the can from the second frustoconical surface.