All of these grenades except the incendiary grenades used the same firing mechanism, and the incendiary grenade firing mechanism was the standard one modified in a single particular. The earliest American requirement in this production was for defensive grenades, of the fragmentation type. Our first estimate was that we would need 21,000,000 of these for actual warfare and 2,000,000 of the unloaded type for practice and training work. But, as the war continued and the American plans developed in scale, we saw we would require a much greater quantity than this; and orders were finally placed for a total of 68,000,000 live grenades and over 3,000,000 of the practice variety. By August 20, 1917, the Trench Warfare Section had developed the design and the drawings for the defensive grenade. The first contract--for 5,000 grenades--was let to the Caskey-Dupree Co. of Marietta, Ohio. This concern was fairly entitled to such preference, because the experimentation leading up to the design for this bomb was conducted almost entirely at its plant in Marietta. Next came an interesting industrial development by a well-known American concern which had previously devoted its exclusive energy to the production of high-grade silverware, but which now, as a patriotic duty, undertook to build the deadly defensive grenades. This was the Gorham Manufacturing Co. of Providence, R. I. This firm contracted to furnish complete, loaded grenades, ready for shipment overseas, and was the only one to build and operate a manufacturing and loading plant. Elsewhere contracts were let for parts only, these parts to converge at the assembling plants later; and such orders were rapidly placed until by the middle of December, 1917, various industrial concerns were tooling up for a total production of 21,000,000 of these missiles. The grenade which these contractors undertook to produce was an American product in its design, although modeled after grenades already in use at the front. Its chief difference was in the firing mechanism, where improvements, or what were then thought to be improvements, had been installed to make it safer in the hands of the soldier than the grenades then in use at the front. This firing mechanism with its pivoted lever was, in fact, a radical departure from European practice. The body of this grenade was of malleable iron, and the grenade exploded with a force greater than that of any in use in France. The remodeling of factories, the building of machines, and the manufacture of tools for this undertaking, pushed forward with determined speed, was completed in from 90 to 120 days, and by April almost all of the companies had reached the stage of quantity production.